CRF Design for Clinical Studies: The Distinct Roles of Data Managers vs Biostatisticians

In medtech clinical trials, the Case Report Form (CRF) is more than a tool for collecting data—it’s the backbone of the study. From capturing critical safety outcomes to evaluating device performance, a well-designed CRF ensures that the study’s goals are met efficiently and reliably.

Achieving this balance requires input from two key roles: the data manager and the biostatistician. While their contributions may overlap in some areas, these roles serve distinct and complementary purposes. Understanding how these professionals work together can help medtech sponsors avoid common pitfalls in CRF design and maximise the success of their trials.

The Data Manager’s Role in CRF Design

Data managers are experts in the operational and technical aspects of CRF design. Their role is to ensure that data collection is standardised, consistent, and compliant with relevant guidelines.

Key responsibilities of a data manager include:

  • Formatting CRFs: Ensuring fields are user-friendly and compatible with electronic data capture (EDC) systems.
  • Regulatory Compliance: Aligning CRFs with industry standards such as CDASH (Clinical Data Acquisition Standards Harmonization).
  • Site Usability: Designing forms that facilitate accurate and consistent data entry across multiple trial sites.

For instance, a data manager might ensure that dropdown menus in the CRF prevent free-text responses, reducing the risk of inconsistencies. Their focus is on the practical and technical aspects of data collection.

The Biostatistician’s Role in CRF Design

Biostatisticians, on the other hand, approach CRF design from an analytical perspective. Their focus is on ensuring that the data collected aligns with the study’s endpoints and supports meaningful statistical analysis.

Key responsibilities of a biostatistician include:

  • Aligning Data with Study Objectives: Defining the variables that need to be captured to evaluate the endpoints outlined in the Statistical Analysis Plan (SAP).
  • Variable Definition: Ensuring that collected data supports statistical methods, such as properly coding categorical variables (e.g., mild/moderate/severe).
  • Derived Metrics: Identifying composite or derived variables that must be pre-defined in the CRF to support downstream analysis.

For example, in a post-market study evaluating a vascular device, the biostatistician would ensure that the CRF captures restenosis rates in a format that allows calculation of primary patency—a key endpoint. Their input ensures that no critical data points are overlooked.

Why Both Roles Are Essential to MedTech Trials

Although data managers and biostatisticians work towards the same goal—collecting high-quality data—their approaches and expertise are fundamentally different. Collaboration between these roles is essential for creating CRFs that are both operationally feasible and analytically robust.

1. Preventing Data Gaps

Without biostatistician oversight, CRFs may fail to capture key variables required for endpoint evaluation. For example:

  • In a stent study, a missing field for recording restenosis or target vessel occlusion could render the primary endpoint unanalysable.
  • Failure to specify timepoints for data collection (e.g., 12-month vs. 60-month follow-up) may result in incomplete datasets for secondary analyses.

2. Ensuring Data Compatibility

While data managers ensure that CRFs meet technical and regulatory standards, biostatisticians ensure the data is analyzable. Misalignment in variable formats can lead to delays or errors during analysis. For instance:

  • Categorical variables (e.g., adverse event severity) coded as free text at some sites and numeric values at others can complicate statistical programming.

3. Regulatory-Ready Analysis

In medtech trials, regulatory submissions rely heavily on robust statistical reporting. Biostatisticians ensure that CRFs are designed to collect all data necessary for generating high-quality, compliant analyses. For example:

  • Derived metrics like cumulative incidence rates must be pre-defined in the CRF to avoid regulatory scrutiny over post-hoc adjustments.

Misconceptions About CRF Design in MedTech

A common misconception in medtech trials is that data managers can fully handle CRF design. While data managers are essential for operationalising CRFs, their expertise does not extend to defining the analytical framework needed to support endpoints and hypotheses.

The Risks of Excluding Biostatistician Input

When biostatisticians are excluded from CRF design:

  • Key Variables May Be Missing: Critical fields for evaluating endpoints may be omitted.
  • Data May Be Misaligned: Improperly coded variables can lead to delays during analysis or errors in reporting.
  • Regulatory Challenges May Arise: Incomplete or improperly formatted data can result in regulatory delays or rejection.

By including biostatisticians early in the CRF design process, sponsors can avoid these risks and ensure their study remains on track.

Real-World Example: The Power of Collaboration

Consider a post-market surveillance study for a diagnostic device. The sponsor relies on CRFs to collect data on device performance across real-world clinical settings. Initially, the data manager designed the CRFs to focus on ease of use at the sites. However, the biostatistician identified a critical oversight: the CRFs did not include fields to track device calibration data, a key variable for assessing long-term performance trends. By collaborating, the data manager and biostatistician ensured the CRFs met both operational and analytical requirements, setting the stage for a successful regulatory submission.

Practical Steps for MedTech Sponsors

To ensure robust CRF design in your medtech trial, consider these steps:

  1. Involve Biostatisticians Early: Engage your biostatistician during the CRF design phase to define variables and ensure alignment with study endpoints.
  2. Foster Collaboration: Encourage close communication between data managers and biostatisticians to balance operational efficiency with analytical rigor.
  3. Prioritise Regulatory Readiness: Design CRFs with regulatory requirements in mind to avoid costly delays during submission.

Final Thoughts

In medtech clinical trials, the success of your study depends on more than just collecting data—it depends on collecting the right data in the right way. Data managers and biostatisticians each bring unique expertise to CRF design, and their collaboration ensures that your trial is set up for operational efficiency, analytical validity, and regulatory success.

By recognising the complementary roles of these professionals, medtech sponsors can avoid common pitfalls and ensure their studies deliver meaningful, actionable results. If you’re planning a clinical trial and want to learn more about how to optimise CRF design, our team at Anatomise Biostats is here to help.

Expert Opinion: Why Biostatistics Qualifications Matter in Med-Tech Industry Clinical Trials.

Consider the consequences if a medical doctor, without a formal medical education or licensing, were to diagnose and treat patients. Such a doctor might misunderstand symptoms, choose the wrong treatments, or even harm patients due to lack of understanding and experience. Similarly, an unqualified biostatistician might incorrectly analyse data, misinterpret statistical significance, or fail to recognise biases and patterns essential for accurate conclusions. These errors, when compounded across studies and publications, create a domino effect, misleading the medical community and affecting clinical guidelines that doctors worldwide follow.

When biostatistics work is flawed due to lack of proper training, the evidence that supports clinical decision-making is compromised. The gravity of these potential errors is amplified because biostatistics underpins clinical trial outcomes, which are often used to secure regulatory approval and define the standards for how to treat diseases. If flawed analysis leads to approving ineffective or harmful treatments, patients could suffer adverse effects from what they believe are safe therapies. In this sense, an unqualified biostatistician is even more dangerous than an unlicensed doctor, as their errors can influence the treatment decisions of countless doctors, each one putting their patients at risk based on incorrect or incomplete data.

Without proper qualifications, a biostatistician’s work can lead to harmful outcomes. This is because the analysis they perform underpins the scientific evidence that doctors rely on to make clinical decisions and guide patient care.


Why a Coursework Masters of Biostatistics an indispensable foundation

High-quality biostatistics programs offer advanced, in-depth training that goes far beyond basic statistical application. One of the core skills instilled is the ability to identify gaps in knowledge and continually adapt to the specific demands of each unique clinical trial. A competent biostatistician isn’t just someone who knows how to apply a set of methods; they are a problem-solver equipped to navigate complex, evolving situations, often needing to research, adapt, or even develop new techniques as each clinical context requires.

Unlike a research-based master’s thesis, which typically hones expertise in a narrow area, a coursework master’s in biostatistics emphasises a broad, structured understanding of the field, preparing individuals to apply statistical techniques accurately in a clinical context. Rigorous training in biostatistics is essential because the stakes are high, and the work of a biostatistician directly influences the treatment approaches trusted by healthcare providers around the world.

A hallmark of a quality biostatistics program is it’s focus on cultivating a mindset of critical evaluation and adaptability. Rather than simply learning a fixed set of methods, students are taught to understand the foundational principles of statistics and how to apply them thoughtfully across different clinical scenarios. This training includes learning how to question assumptions, test the validity of models, and assess the appropriateness of methods in light of each study’s design and data characteristics. It also involves learning how to identify situations where the standard, previously used methods may not suffice—an ability that can only come from a deep understanding of the mathematical principles underpinning statistical techniques.

The mathematical underpinnings of statistical tests can be subtle and intricate. Without specialised training, there’s a high risk that these mathematical nuances will be overlooked or mishandled. For example, failure to correctly adjust for confounding variables can make it appear as though a treatment effect exists when it doesn’t, leading to erroneous conclusions that could harm patients if implemented in clinical practice.

A well-prepared biostatistician is not only familiar with a wide range of statistical tools but also understands when each tool is appropriate, and more importantly, when it may be insufficient. Clinical trials often present unique challenges, such as complex interactions between variables, confounding factors, and datasets that may not conform neatly to traditional statistical models. In these cases, biostatisticians trained to think critically and independently can recognise that the standard approaches may fall short and are capable of researching novel methods, exploring the latest advancements, and adapting techniques to better fit the data at hand. This ability to assess, research, and innovate rather than rigidly apply textbook methods is what makes a biostatistician invaluable to clinical research.

Advanced biostatistics programs emphasise this flexibility, often incorporating coursework in emerging statistical methods, machine learning, and adaptive designs that are becoming increasingly relevant in modern clinical trials. These programs also provide hands-on training with real-world data, equipping students to handle the messy, imperfect datasets typical in clinical research. Graduates from rigorous programs gain the skills needed to work with a high degree of precision, recognising the limitations of each approach and adapting their methods to provide the most reliable analysis possible.

This commitment to continuous learning and adaptability is essential, particularly in a field as fast-evolving as clinical biostatistics. New statistical models, computational methods, and technologies are constantly emerging, offering powerful new ways to analyse data and uncover insights that would be missed with conventional methods. Biostatisticians trained to think critically and assess what they do not yet know are equipped to stay at the forefront of these advancements, ensuring that clinical trial data is analysed with the most effective and current techniques.

Individuals without this specialised training or with training from adjacent fields may lack this advanced skill set. While they may be familiar with statistical software and certain techniques, they often lack the deeper statistical grounding that allows them to identify gaps in their own knowledge, research novel techniques, and apply methods flexibly. They may rely more heavily on familiar, pre-existing methods, even when these approaches are suboptimal for the specific demands of a new clinical trial.

In clinical research, it’s critical to distinguish between fields that may seem related to biostatistics but lack the specialised training needed for rigorous clinical trial analysis. Adjacent disciplines such as biomedical engineering or bioinformatics, while valuable in their own right, do not provide the depth and specificity of statistical training required for high-stakes clinical biostatistics. Clinical trials demand a comprehensive understanding of advanced statistical methods, hypothesis testing, probability theory, and the practical challenges inherent in real-world clinical data. Without this foundation, there is a high risk that even a highly skilled professional in an adjacent field may misinterpret trial data or apply suboptimal models, potentially jeopardising trial results.

While adjacent fields like biomedical engineering and bioinformatics serve as valuable components to clinical research teams, they do not replace a biostatistician in terms of the depth of statistical expertise required to conduct clinical trials safely and effectively. Additionally, even within biostatistics itself, the rigour and quality of training can vary widely between institutions. A high-quality biostatistics qualification, grounded in coursework and practical experience, is essential to ensure that biostatisticians are fully prepared to meet the demands of clinical trial analysis, providing reliable evidence that healthcare providers can depend on to guide safe, effective patient care.


Core statistical concepts: Beyond Basic Stats


When we think about clinical trials, we often picture doctors, patients, and maybe lab scientists—but behind every trial is a biostatistician. They’re responsible for interpreting the data in a way that uncovers whether a treatment truly works, and just as importantly, whether it’s safe. On the surface, this might sound like standard statistics, but the reality is far more complex. Clinical trials involve intricate designs, variable data, and outcomes that hinge on precisely the right analytical approach. Here’s why a biostatistician needs a Master’s degree in biostatistics to navigate this terrain.


The Power Calculation: Not Just Plugging in Numbers

One of the most fundamental tasks in clinical trials is calculating statistical power—essentially, determining the sample size required to detect a treatment effect if it exists. While it might sound as simple as choosing a sample size, calculating power is actually a multi-layered process, filled with nuances that require advanced training.

A biostatistician needs to understand how effect size, variability, sample size, and study design all interact. For instance, they can’t simply use a pre-set formula; they must examine assumptions about the patient population, factor in dropout rates, and sometimes even simulate different scenarios to see how robust their sample size calculation is. If the sample size is too small, the study could miss a true treatment effect, leading to the incorrect conclusion that a treatment is ineffective. Too large, and it wastes resources and could expose patients to unnecessary risk.

An advanced biostatistics program should explore how to conduct sensitivity analyses, interpret simulation results, and understand the trade-offs in different power calculation approaches. These skills can be impractical to cultivate on the job without a solid foundation.


Hypothesis Testing: Far More Than Just a P-value

Hypothesis testing often gets reduced to p-values, but in clinical trials, p-values are just the tip of the iceberg. Deciding how to structure a hypothesis test is a skill that requires an in-depth understanding of the trial design, data type, and statistical limitations. P-values themselves are affected by factors like sample size and effect size, and they depend on correct assumptions about the data. If these assumptions are even slightly off, the results could be misleading. Additionally, a significant p value is not necessarily clinically meaningful – an effect size must be carefully considered.

Suppose a trial includes multiple subgroups, such as different age ranges, where treatment response might vary. A biostatistician needs to decide whether to test each group separately or combine them, taking into account the risk of inflating the false positive rate. They may have to employ adjustments like the Bonferroni correction or false discovery rate, each with its own implications for the results’ reliability. Knowing when and how to apply these adjustments requires expertise in statistical trade-offs—a skill set that goes beyond basic training.


Bayesian Modelling: The Complexity of Integrating Prior Information

In clinical trials, Bayesian modelling offers the flexibility to incorporate prior information, which can be crucial when there’s existing data on similar treatments. But building a Bayesian model is not as simple as adding a prior and letting the data “speak.” Bayesian analysis is an iterative, highly contextual process that involves understanding the nuances of prior selection, data updates, and model convergence.

For example, in a trial with limited data, the biostatistician might consider a prior based on past studies. But they need to ensure that the prior doesn’t overpower the current data, especially if the populations differ in meaningful ways. They’ll also have to assess how sensitive the model is to the chosen prior—small changes can have a large impact on the results. Once the model is built, they will test it with simulations, iteratively refine their approach, and apply computational techniques like Markov Chain Monte Carlo methods to ensure accurate estimates.

Core skills include how to choose and validate priors, handle computational challenges, and interpret Bayesian results in a way that is both statistically valid and clinically meaningful. Without this background, Bayesian methods could be misapplied, leading to conclusions that are overly dependent on prior data, potentially skewing the trial’s findings.


Handling Confounding Variables: Getting to the True Treatment Effect

Confounding variables are one of the most significant challenges in clinical trials. These are external factors that could influence both the treatment and the outcome, creating a false impression of effect. Managing confounding variables isn’t as simple as throwing all variables into a model. It involves selecting the right approach—whether that’s stratification, regression adjustment, or propensity score matching—to isolate the treatment’s actual impact.

Imagine a trial assessing the effect of a heart medication where younger patients tend to recover faster. If age isn’t properly accounted for, the results might suggest that the treatment is effective, simply because younger patients are overrepresented in the treatment group. Handling such confounding factors involves understanding the dependencies between variables, testing assumptions, and assessing the adequacy of different adjustment techniques.

Biostatistics programs address these complexities, teaching biostatisticians how to identify and handle confounders, use advanced models like inverse probability weighting, and validate their adjustments with sensitivity analyses. This is not something that can be mastered without a solid foundation in statistics and it’s application to medicine.

A practical example:


Consider a clinical trial evaluating an innovative cardiac monitoring device intended to reduce adverse cardiovascular events in a diverse patient population, with participants spanning a wide range of ages, co-morbidities, and cardiovascular risk profiles. The complexity of this study lies not only in the heterogeneity of the patient population but also in the need to accurately capture the device’s effectiveness over extended time periods and in varied real-world contexts. Here, standard statistical methods may fail to capture the full picture; without careful investigation and adaptation, these methods could miss critical variations in device effectiveness across different patient subgroups. Missteps in analysis could lead to misguided conclusions, resulting in the misapplication of the device or failure to recognise its specific benefits for certain populations.

An unqualified biostatistician, seeing only the broad structure of the trial, might select standard statistical approaches such as repeated measures analysis or proportional hazards models, assuming that the device’s impact can be summarised uniformly across patients and time. These methods, while effective in certain contexts, may oversimplify the true complexity of the data. For instance, these approaches may overlook significant patient-specific variations, assuming all patients respond similarly over time, and fail to address potential dependencies across repeated measurements. In doing so, they risk obscuring insights into how the device performs across age groups, co-morbidity profiles, or geographic regions.

A competent biostatistician, however, would recognise that such a complex, dynamic scenario demands a more tailored and investigative approach. They would start by reviewing trial specifics—population diversity, data structure, and endpoints—and identifying the particular challenges these present. This initial assessment might lead them to consider a range of advanced modelling techniques, from hierarchical models and frailty models to time-varying covariate models, evaluating each option to find the best fit for the study’s unique demands.

For instance, a hierarchical model could capture variability at multiple levels—such as individual patients, treatment centres, or geographic clusters—allowing the biostatistician to account for factors that might cluster within sites or subgroups. If, for example, patients from one geographic area tend to experience more adverse events, a hierarchical model would help isolate these effects, ensuring they don’t skew the treatment outcomes. A frailty model, on the other hand, might be more appropriate if there are unobserved variables influencing patient outcomes, such as genetic predispositions or lifestyle factors that impact how individuals respond to the device. Each model offers benefits but comes with specific assumptions and limitations, requiring the biostatistician to weigh these factors carefully.

The biostatistician would then move beyond selecting a method, entering a phase of critical evaluation and testing. They perform model diagnostics to check assumptions, such as independence and proportional hazards, assessing how well each model fits the trial data. If they find that patient characteristics change over time, influencing treatment response, they may pivot toward a time-varying covariate model. Such a model could capture how the effectiveness of the device changes with patient health fluctuations, an essential insight in trials where health status is dynamic. Rather than assuming proportional effects across time, this approach would allow the analysis to reflect real-world shifts in patient health and co-morbidity, enhancing the relevance of the results for long-term patient care.

In addition, the biostatistician may implement advanced stratification techniques or subgroup analyses, aiming to parse out the effects of specific co-morbidities like diabetes or chronic kidney disease. These approaches are not simply a matter of segmenting data; they require careful control of confounding variables and an understanding of how stratification affects power and interpretation. The biostatistician could explore techniques such as propensity score weighting or covariate balancing to create comparable subgroups, helping to isolate the device’s effect on each subgroup with minimal bias. This ensures that the treatment effect estimation is not conflated with unrelated patient characteristics, like age or pre-existing health conditions, which could distort the true efficacy of the device.

Because of the trial’s longitudinal design, the biostatistician would also need to research and carefully apply methods that accommodate time-dependent covariates. They might examine the appropriateness of flexible parametric survival models over the traditional Cox model, especially if patient health or response to treatment fluctuates significantly over time. By reviewing the latest literature and comparing models through simulation studies, the biostatistician can determine which methods best capture the time-varying nature of the data without introducing artefacts or biases. For instance, a flexible model might reveal periods during which the device is particularly effective, or it could show diminishing efficacy as patients’ health profiles evolve, offering critical insights into when and for whom the device provides the most benefit.

In this rigorous process, the biostatistician doesn’t simply apply methods—they conduct an iterative investigation, refining their approach with each step. Sensitivity analyses, for example, might be run to determine how robust findings are to different modelling choices or to evaluate the impact of unmeasured confounders. Through this iterative process, they test assumptions, explore the validity of each approach, and adjust techniques to ensure that their final analysis captures the device’s effectiveness in a nuanced, clinically relevant way. This stands in contrast to a one-size-fits-all analysis, where insights into key variations across patient subgroups may be lost.

Ultimately, the advanced approach adopted by a qualified biostatistician goes beyond statistical rigour—it provides a comprehensive, meaningful picture of the device’s real-world effectiveness. By thoroughly investigating and validating each method, the biostatistician ensures that their analysis accurately reflects how the device performs across diverse patient populations. This depth of analysis provides doctors with reliable, specific insights into which patients are most likely to benefit, supporting safer, more personalised treatment decisions in real-world clinical settings.

Biometrics & Clinical Trials Success:

Why Outsourcing a Biostatistics Team is Pivotal to the Success of your Clinical Trial

Clinical trials are among the most critical phases in bringing a medical device or pharmaceutical product to market, and ensuring the accuracy and integrity of the data generated is essential for success. While some companies may feel confident relying on their internal teams, especially if they have expertise in AI or data science, managing the full scope of biometrics in clinical trials often requires far more specialised skills. Building a dedicated in-house team may seem like a natural next step, but it can involve significant time, cost, and resource investment that can sometimes be underestimated.

Outsourcing biometrics services offers a streamlined, cost-effective alternative, providing access to a team of specialists in statistical programming, quality control, and regulatory compliance. Much like outsourcing marketing or legal services, entrusting biometrics to an external team allows businesses to focus on their core strengths while ensuring the highest standards of data accuracy and regulatory alignment. In this article, we explore why outsourcing biometrics is a smarter approach for clinical trials, offering the expertise, flexibility, and scalability needed to succeed.

1. Expertise Across Multiple Disciplines

Clinical trials require a blend of specialised skills, from statistical programming and data management to quality control and regulatory compliance. Managing these diverse requirements internally can stretch resources and may lead to oversights. When outsourcing to a biometrics team, companies can access a broad range of expertise across all these critical areas, ensuring that every aspect of the trial is handled by specialists in their respective fields.

Instead of spreading resources thin across a small internal team, outsourcing offers a more efficient approach where every key area is covered by experts, ultimately reducing the risk of errors and enhancing the quality of the trial data.


2. Avoid Bottlenecks and Delays

Managing the data needs of a clinical trial requires careful coordination, and internal teams can sometimes face bottlenecks due to workload or resource limitations. Unexpected delays, such as staff absences or project overload, can slow progress and increase the risk of missed deadlines.

Outsourcing provides built-in flexibility, where a larger, more experienced team can step in when needed, ensuring work continues without interruption. This kind of seamless handover keeps the trial on track and avoids the costly delays that might arise from trying to juggle too many responsibilities in-house.


3. Improved Data Quality Through Redundancy

One of the advantages of outsourcing biometrics is the added level of redundancy it offers. In-house teams, particularly small ones, may not have the capacity for thorough internal quality checks, potentially allowing errors to slip through.

Outsourced teams typically have multiple layers of review built into their processes. This ensures that data undergoes several levels of scrutiny, significantly reducing the risk of unnoticed mistakes and increasing the overall reliability of the analysis.


4. Flexibility and Scalability

The nature of clinical trials often shifts, with new sites, additional data points, or evolving regulatory requirements. This creates a demand for scalability in managing the trial’s data. Internal teams can struggle to keep up as the project grows, sometimes leading to bottlenecks or rushed work that compromises quality.

Outsourcing biometrics allows companies to adapt to the changing scope of a trial easily. A specialised team can quickly scale its operations to handle additional workload without compromising the timeline or quality of the analysis.


5. Ensuring Regulatory Compliance

Meeting regulatory requirements is a critical aspect of any clinical trial. From meticulous data documentation to adherence to best practices, there are stringent standards that must be followed to gain approval from bodies like the FDA or EMA.

Outsourcing to an experienced biometrics team ensures that these standards are met consistently. Having worked across multiple trials, outsourced teams are well-versed in the latest regulations and can ensure that all aspects of the trial meet the necessary compliance requirements. This reduces the risk of costly rejections or trial delays caused by non-compliance.


6. Enhanced Data Security and Infrastructure

Handling sensitive clinical trial data requires secure systems and advanced infrastructure, which can be costly for companies to manage internally. Maintaining this infrastructure, along with the necessary cybersecurity measures, can quickly escalate expenses, especially for smaller in-house teams.

By outsourcing biometrics, companies gain access to teams with pre-existing secure infrastructure designed specifically for clinical data. This not only reduces costs but also mitigates the risk of data breaches, ensuring compliance with privacy regulations like GDPR.


7. Hidden Challenges of Building an In-House Team

While building an in-house biometrics team might seem appealing, it comes with it’s hidden challenges and costs that are easily overlooked. Recruitment, training, administrative load and retention all contribute to a growing budget, along with HR costs and the ongoing need to invest in tools and advanced infrastructure to keep the team effective.

Outsourcing offers a clear financial benefit here. Companies can bypass many resource draining activities and gain immediate access to a team of experts, without having to worry about ongoing staff management or the investment in specialised tools.


8. Unbiased Expertise

Internal teams may face pressure to align with existing company practices or preferences, which can sometimes lead to biased decisions when it comes to methodology or quality control. Outsourced teams are entirely independent and focused solely on delivering objective, high-quality results. This ensures that the best statistical methods are applied, without the potential for internal pressures to sway critical decisions.


The Case for Outsourcing Biometrics

Clinical trials are complex and require a range of specialised skills to ensure their success. While building an in-house team might seem like an intuitive solution, it often introduces unnecessary risks, hidden costs, and logistical challenges. Outsourcing biometrics to a specialised team offers a streamlined, scalable solution that ensures trial data is handled with precision and integrity, while maintaining regulatory compliance.

By leveraging the expertise of an external biometrics team, companies can focus on their core strengths—whether it’s developing a breakthrough medical device or innovating in their field—while leaving the complexities of biometrics to the experts.


If you’re preparing for your next clinical trial and want to ensure
reliable, accurate, and compliant results, contact Anatomise Biostats
today. Our expert biometrics team is ready to support your project
and deliver the results you need to bring your medical device to
market with confidence.


The Role of Clinical-Translational Studies in Validation of Diagnostic Devices

Clinical-translational studies refer to research studies that bridge the gap between early-stage diagnostic development and real-world clinical application. In a diagnostics context these studies focus on translating promising diagnostic technologies from laboratory research (preclinical stage) to clinical practice, where they can be validated, assessed for clinical utility, and eventually integrated into routine healthcare settings.

The primary goal of clinical-translational studies for diagnostics is to evaluate the performance, accuracy, safety, and overall effectiveness of new diagnostic tests or devices in real-world patient populations. These studies play a critical role in determining whether the diagnostic technology can reliably detect specific diseases or conditions, guide treatment decisions, improve patient outcomes, and enhance the overall healthcare experience.

Key Characteristics of Clinical-Translational Studies for Diagnostics:

Validation of Diagnostic Accuracy:
In clinical-translational studies, diagnostic accuracy and reliability is rigorously validated. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) are assessed to determine how effectively the diagnostic test can identify true positive and true negative cases. These metrics provide essential insights into the precision and reliability of the test’s performance.

Clinical Utility Evaluation:
Beyond accuracy, clinical-translational studies focus on evaluating the clinical utility of the diagnostic technology. The impact of the test on patient management, treatment decisions, and overall healthcare outcomes is carefully assessed. Real-world data is analysed to understand how the test guides appropriate clinical actions and leads to improved patient outcomes. This evaluation helps stakeholders better assess the value of the diagnostic test in clinical practice.

Inclusion of Diverse Patient Populations:
Clinical-translational studies encompass a wide range of patient populations to ensure the generalisability of the diagnostic test’s results. Studies are designed to include patients with various demographics, medical histories, and disease severities, making the findings applicable to real-world scenarios. Robust statistical analyses are employed to identify potential variations in test performance across different patient groups, enhancing the diagnostic test’s inclusivity and practicality.

Comparative Analyses:
In certain cases, comparative analyses are conducted in clinical-translational studies to evaluate the performance of the new diagnostic technology against existing standard-of-care tests or reference standards. Differences in accuracy and clinical utility are quantified using statistical methods, enabling stakeholders to make informed decisions regarding the adoption of the new diagnostic test or device.

Use of Real-World Evidence:
Real-world evidence plays a pivotal role in clinical-translational studies. Data from routine clinical practice settings are collected to assess the test’s performance under authentic healthcare conditions. Advanced statistical techniques are employed to analyse real-world data, providing valuable insights into how the diagnostic test performs in real patient populations. This evidence informs the adoption and implementation of the test in clinical practice.

Compliance with Regulatory Guidelines:
Compliance with regulatory guidelines and standards is essential for the success of clinical-translational studies. Studies are designed and conducted following regulatory requirements set by health authorities, ensuring adherence to Good Clinical Practice (GCP) guidelines and ethical considerations to ensure data quality and to protect patient safety and privacy.

Conducting Longitudinal Studies:
For certain diagnostic technologies, particularly those used for monitoring or disease progression, longitudinal studies may be necessary. These studies are designed to assess the diagnostic device’s performance over time and identify potential variations or trends. Longitudinal analyses enable researchers to understand how the diagnostic test performs in the context of disease progression and treatment response.

Interdisciplinary Collaboration:
Clinical-translational studies involve collaboration among diverse stakeholders, such as clinicians, biostatisticians, regulatory experts, and industry partners. Biostatisticians play a pivotal role in facilitating effective communication and coordination among team members. This interdisciplinary collaboration ensures that all aspects of the research, from study design to data analysis and interpretation, are conducted with precision and expertise.

Clinical-translational studies in diagnostics demand a comprehensive and multidisciplinary approach, where biostatisticians play a vital role in designing robust studies, analysing complex data, and providing valuable insights. Through these studies, diagnostic technologies can be validated, and their clinical relevance can be determined, ultimately leading to improved patient care and healthcare outcomes.

For more information on our services for clinical-translational studies see here.

Stata: Statistical Software for Regulatory Compliance in Clinical Trials

Stata is widely used in various research domains such as economics, biosciences, health and social sciences, including clinical trials. It has been utilised for decades in studies published in reputable scientific journals. While SAS has a longer history of being explicitly referenced by regulatory agencies such as the FDA, Stata can still meet regulatory compliance requirements in clinical trials. StataCorp actively engages with researchers, regulatory agencies, and industry professionals to address compliance needs and provide technical support, thereby maintaining a strong commitment to producing high-quality software and staying up to date with industry standards.

Stata’s commitment to accuracy, comprehensive documentation, integrated versioning, and rigorous certification processes provides researchers with a reliable and compliant statistical software for regulatory submissions. Stata’s worldwide reputation, excellent technical support, seamless verification of data integrity, and ease of obtaining updates further contribute to its suitability for clinical trials and regulatory compliance.

To facilitate regulatory compliance in clinical trials, Stata offers features such as data documentation and audit trails, allowing researchers to document and track data manipulation steps for reproducibility and transparency. Stata’s built-in “do-files” and “log-files” can capture commands and results, aiding in the audit trail process. Stata provides the flexibility to generate analysis outputs and tables in formats commonly required for regulatory reporting (e.g., PDF, Excel, or CSV). It also enables the automation of reproducible, fully-formatted publication standard reports. Strong TLF and CRF programming used to be the domain of SAS which explains their early industry dominance. SAS was developed in 1966 using funding from the National Institute of Health. In recent years, however, Stata has arguably surpassed what is achievable in SAS with the same efficiency, particularly in the context of clinical trials.

Stata has extensive documentation of adaptive clinical trial design. Adaptive group sequential designs can be achieved using the GDS functionality. The default graphs and tables produced using GDS analysis really do leave SAS in the dust being more visually appealing and easily interpretable. They are also more highly customisable than what can be produced in SAS. Furthermore the Stata syntax used to produce them is minimal compared to corresponding SAS commands, while still retaining full reproducibility.

Stata’s comprehensive causal inference suite enables experimental-style causal effects to be derived from observational data. This can be helpful in planning clinical trials based on observed patient data that is already available, with the process being fully documentable.

Advanced data science methods are being increasingly used in clinical trial design and planning as well as for follow-up exploratory analysis of clinical trial data. Stata has both supervised and unsupervised machine learning capability in its own right for decades. Stata can also integrate with other tools and programming languages, such as Python for PyStata and PyTrials, if additional functionalities or specific formats are needed. This can be instrumental for advanced machine learning and other data science methods goes beyond native features and user-made packages in terms of customisability. Furthermore, using Python within the Stata interface allows for compliant documentation of all analyses. Python integration is also available in SAS via numerous packages and is able to eliminate some of the limitations of native SAS, particularly when it comes to graphical outputs.

Stata for FDA regulatory compliance

While the FDA does not mandate the use of any specific statistical software, they emphasise the need for reliable software with appropriate documentation of testing procedures. Stata satisfies the requirements of the FDA and is recognized as one of the most respected and validated statistical tools for analysing clinical trial data across all phases, from pre-clinical to phase IV trials. With Stata’s extensive suite of statistical methods, data management capabilities, and graphics tools, researchers can rely on accurate and reproducible results at every step of the analysis process.

When it comes to FDA guidelines on statistical software, Stata offers features that assist in compliance. Stata provides an intuitive Installation Qualification tool that generates a report suitable for submission to regulatory agencies like the FDA. This report verifies that Stata has been installed properly, ensuring that the software meets the necessary standards.

Stata offers several key advantages when it comes to FDA regulatory compliance for clinical trials. Stata takes reproducibility seriously and is the only statistical package with integrated versioning. This means that if you wrote a script to perform an analysis in 1985, that same script will still run and produce the same results today. Stata ensures the integrity and consistency of results over time, providing reassurance when submitting applications that rely on data and results from clinical trials.

Stata also offers comprehensive manuals that detail the syntax, use, formulas, references, and examples for all commands in the software. These manuals provide researchers with extensive documentation, aiding in the verification and validity of data and analyses required by the FDA and other regulatory agencies.

To further ensure computational validity, Stata undergoes extensive software certification testing. Millions of lines of certification code are run on all supported platforms (Windows, Mac, Linux) with each release and update. Any discrepancies or changes in results, output, behaviour, or performance are thoroughly reviewed by statisticians and software engineers before making the updated software available to users. Stata’s accuracy is also verified through the National Institute of Standards (NIST) StRD numerical accuracy tests and the George Marsaglia Diehard random-number generator tests.

Data management in Stata

Stata’s Datasignature Suite and other similar features offer powerful tools for data validation, quality control, and documentation. These features enable users to thoroughly examine and understand their datasets, ensuring data integrity and facilitating transparent research practices. Let’s explore some of these capabilities:

  1. Datasignature Suite:

The Datasignature Suite is a collection of commands in Stata that assists in data validation and documentation. It includes commands such as `datasignature` and `dataex`, which provide summaries and visualizations of the dataset’s structure, variable types, and missing values. These commands help identify inconsistencies, outliers, and potential errors in the data, allowing users to take appropriate corrective measures.

2. Variable labelling:

 Stata allows users to assign meaningful labels to variables, enhancing data documentation and interpretation. With the `label variable` command, users can provide descriptive labels to variables, making it easier to understand their purpose and content. This feature improves collaboration among researchers and ensures that the dataset remains comprehensible even when shared with others.

3. Value labels:

 In addition to variable labels, Stata supports value labels. Researchers can assign descriptive labels to specific values within a variable, transforming cryptic codes into meaningful categories. Value labels enhance data interpretation and eliminate the need for constant reference to codebooks or data dictionaries.

4. Data documentation:

Stata encourages comprehensive data documentation through features like variable and dataset-level documentation. Users can attach detailed notes and explanations to variables, datasets, or even individual observations, providing context and aiding in data exploration and analysis. Proper documentation ensures transparency, reproducibility, and facilitates data sharing within research teams or with other stakeholders.

5. Data transformation:

Stata provides a wide range of data transformation capabilities, enabling users to manipulate variables, create new variables, and reshape datasets. These transformations facilitate data cleaning, preparation, and restructuring, ensuring data compatibility with statistical analyses and modelling procedures.

6. Data merging and appending:

Stata allows users to combine multiple datasets through merging and appending operations. By matching observations based on common identifiers, researchers can consolidate data from different sources or time periods, facilitating longitudinal or cross-sectional analyses. This feature is particularly useful when dealing with complex study designs or when merging administrative or survey datasets.

7. Data export and import:

Stata offers seamless integration with various file formats, allowing users to import data from external sources or export datasets for further analysis or sharing. Supported formats include Excel, CSV, SPSS, SAS, and more. This versatility enhances data interoperability and enables collaboration with researchers using different software.

These features collectively contribute to data management best practices, ensuring data quality, reproducibility, and documentation. By leveraging the Datasignature Suite and other data management capabilities in Stata, researchers can confidently analyse their data and produce reliable results while maintaining transparency and facilitating collaboration within the scientific community.

Stata and maintaining CDISC standards. How does it compare to SAS?

Stata and SAS are both statistical software packages commonly used in the fields of data analysis, including in the pharmaceutical and clinical research industries. While they share some similarities, there are notable differences between the two when it comes to working with CDISC standards:

  1. CDISC Support:

SAS has extensive built-in support for CDISC standards. SAS provides specific modules and tools, such as SAS Clinical Standards Toolkit, which offer comprehensive functionalities for CDASH, SDTM, and ADaM. These modules provide pre-defined templates, libraries, and validation rules, making it easier to implement CDISC standards directly within the SAS environment. Stata, on the other hand, does not have native, dedicated modules specifically designed for CDISC standards. However, Stata’s flexibility allows users to implement CDISC guidelines through custom programming and data manipulation.

2. Data Transformation:

SAS has robust built-in capabilities for transforming data into SDTM and ADaM formats. SAS provides specific procedures and functions tailored for SDTM and ADaM mappings, making it relatively straightforward to convert datasets into CDISC-compliant formats. Stata, while lacking specific CDISC-oriented features, offers powerful data manipulation functions that allow users to reshape, merge, and transform datasets. Stata users may need to develop custom programming code to achieve CDISC transformations.

3. Industry Adoption:

SAS has been widely adopted in the pharmaceutical industry and is often the preferred choice for CDISC-compliant data management and analysis. Many pharmaceutical companies, regulatory agencies, and clinical research organizations have established workflows and processes built around SAS for CDISC standards. Stata, although less commonly associated with CDISC implementation, is still a popular choice for statistical analysis across various fields, including healthcare and social sciences. Stata has the potential to make adherence to CDISC standards a more affordable option for small companies and therefore an increased priority.

4. Learning Curve and Community Support:

SAS has a long been the default preference in the context of CDISC compliance and is what statistical programmers are used to, thus SAS is known for its comprehensive documentation and extensive user community. Resources including training materials, user forums, and user groups, which can facilitate learning and support for CDISC-related tasks. Stata also has an active user community and provides detailed documentation, but its community may be comparatively smaller in the context of CDISC-specific workflows. Stata has the advantage of reducing the amount of programming required to achieve CDISC compliance, for example in the creation of SDTM and ADaM data sets.

While SAS offers dedicated modules and tools specifically designed for CDISC standards, Stata provides flexibility and powerful data manipulation capabilities that can be leveraged to implement CDISC guidelines. The choice between SAS and Stata for CDISC-related work may depend on factors such as industry norms, organizational preferences, existing infrastructure, and individual familiarity with the software.

While SAS has historically been more explicitly associated with regulatory compliance in the clinical trial domain, Stata is fully equipped to fulfil regulatory requirements and has been utilised effectively in clinical research since. Researchers often choose the software they are most comfortable with and consider factors such as data analysis capabilities, familiarity, and support when deciding between SAS and Stata for their regulatory compliance needs.

It is important to note that compliance requirements can vary based on specific regulations and guidelines. Researchers are responsible for ensuring their analysis and reporting processes align with the appropriate regulatory standards and should consult relevant regulatory authorities when necessary.

The Devil’s Advocate: Stata for Clinical Study Design, Data Processing, & Statistical Analysis of Clinical Trials.

Stata is a powerful statistical analysis software that offers some advantages for clinical trial and medtech use cases compared to the more widely used SAS software. Stata provides an intuitive and user-friendly interface that facilitates efficient data management, data processing and statistical analysis. Its agile and concise syntax allows for reproducible and transparent analyses, enhancing the overall research process with more readily accessible insights.

Distinct from R, which incorporates S based coding, both Stata and SAS have used C based programming languages since 1985.  All three packages can parse full Python within their environment for advanced machine learning capabilities, in addition to those available natively. In Stata’s case this is achieved through the pystata python package. Despite a common C based language, there are tangible differences between Stata and SAS syntax. Stata generally needs less lines of code on average compared to SAS to perform the same function and thus tends to be more concise. Stata also offers more flexibility to how you code as well as more informative error statements which makes debugging a quick and easy process, even for beginners.

When it comes to simulations and more advanced modelling our experience had been that the Basic Edition of Stata (BE) is faster and uses less memory to perform the same task compared to Base SAS. Stata BE certainly has more inbuilt capabilities than you would ever need for the design and analysis of advanced clinical trials and sophisticated statistical modelling of all types. There is also the additional benefit of thousands of user-built packages, such as the popular WinBugs, that can be instantly installed as add-ons at no extra cost. Often these packages are designed to make existing Stata functions even more customisable for immense flexibility and programming efficiency.  Both Stata and SAS represent stability and reliability and have enjoyed widespread industry adoption. SAS has been more widely adopted by big pharma and Stata more-so with public health and economic modelling. 

It has been nearly a decade since the Biostatistics Collaboration of Australia (BCA) which determines Biostatistics education nationwide has transitioned from teaching SAS and R as part of their Masters of Biostatistics programs to teaching Stata and R. This transition initially was made in anticipation of an industry-wide shift from SAS to Stata. Whether their predictions were accurate or not, the case for Stata use in clinical trials remains strong.

Stata is almost certainly a superior option for bootstrapped life science start-ups and SMEs. Stata licencing fees are in the low hundreds of pounds with the ability to quickly purchase over the Stata website, while SAS licencing fees span the tens to hundreds of thousands and often involve a drawn-out process just to obtain a precise quote.

Working with a CRO that is willing to use Stata means that you can easily re-run any syntax provided from the study analysis to verify or adapt it later. Of course, open-source software such as R is also available, however Stata has the advantage of a reduced learning curve being both user-friendly and sufficiently sophisticated.

Stata for clinical trials

  1. Industry Adoption:

Stata has gained significant popularity and widespread adoption in the field of clinical research. It is commonly used by researchers, statisticians, and healthcare professionals for the statistical analysis of clinical data.

2. Regulatory Compliance and CDISC standardisation:

Stata provides features and capabilities that support regulatory compliance requirements in clinical trials. While it may not have the same explicit recognition from CDISC as SAS, Stata does lend itself well to CDISC compliance and offers tools for documentation, data tracking, and audit trails to ensure transparency and reproducibility in analyses.

3. Comprehensive Statistical Procedures:

A key advantage of Stata is its extensive suite of built-in statistical functions and commands specifically designed for clinical trial data analysis. Stata offers a wide range of methods for handling missing data, performing power calculations, and of course a wide range of methods for analysing clinical trial data; from survival analysis methods, generalized linear models, mixed-effects models, causal inference, and Bayesian simulation for adaptive designs. Preparatory tasks for clinical trials such as meta-analysis, sample size calculation and randomisation schedules are arguably easier to achieve in Stata than SAS. These built-in functionalities empower researchers to conduct various analyses within a single software environment.

4. Efficient Data Management:

Stata excels in delivering agile data management capabilities, enabling efficient data handling, cleaning, and manipulation. Its intuitive data manipulation commands allow researchers to perform complex transformations, merge datasets, handle missing data, and generate derived variables seamlessly.

Perhaps the greatest technical advantage of Stata over SAS in the context of clinical research is usability and greater freedom to keep open and refer to multiple data sets with multiple separate analyses at the same time. While SAS can keep many data sets in memory for a single project, Stata can keep many data sets in siloed memory for simultaneous use in different windows to enable viewing or working on many different projects at the same time. This approach can make workflow easier because no data step is required to identify which data set you are referring to, instead the appropriate sections of any data sets can be merged with the active project as needed and due to siloing, which works similarly to tabs in a browser, you do not get the log, data or output of one project mixed up with another. This is arguably an advantage for biostatisticians and researchers alike who typically do need to compare unrelated data sets or the statistical results from separate studies side-by-side.

5. Interactive and Reproducible Analysis:

Stata provides an interactive programming environment that allows users to perform data analysis in a step-by-step manner. The built-in “do-file” functionality facilitates reproducibility by capturing all commands and results, ensuring transparency and auditability of the analysis process. The results and log window for each data set prints out the respective syntax required item by item. This syntax can easily be pasted into the do-file or the command line to edit or repeat the command with ease. SAS on the other hand tends to separate the results from the syntax used to derive it.

6. Graphics and Visualization:

While not traditionally known for this, Stata actually offers a wide range of powerful and customizable graphical capabilities. Researchers can generate high-quality publication standard  plots and charts of any description needed to visualise clinical trial results Common examples include survival curves, forest plots, spaghetti and diagnostic plots. Stata also has built-in options to perform all necessary assumption and model checking for statical model development.

These visualisations facilitate the exploration and presentation of complex data patterns, as well as the presentation, and communication of findings. There are many user-created customisation add-ons for data visualisation that rival what is possible in R customisation.

The one area of Stata that users may find limiting is that it is only possible to display one graph at a time per active data set. This means that you do need to copy graphs as they are produced and save them into a document to compare multiple graphs side by side.

7. Active User Community and Support:

Like SAS, Stata has a vibrant user community comprising researchers, statisticians, and experts who actively contribute to discussions, share knowledge, and provide support. StataCorp, the company behind Stata, offers comprehensive documentation, online resources, and user forums, ensuring users have access to valuable support and assistance when needed. Often the resources available for Stata are more direct and more easily searchable than what is available for SAS when it comes to solving customisation quandaries. This is of course bolstered by the availability of myriad instant package add-ons.

Stata’s active and supportive user community is a notable advantage. Researchers can access extensive documentation, online forums, and user-contributed packages, which promote knowledge sharing and facilitate problem-solving. Additionally, Stata’s reputable technical support ensures prompt assistance for any software-related queries or challenges.

While SAS and Stata have their respective strengths, Stata’s increasing industry adoption, statistical capabilities, data management features, reproducibility, visualisation add-ons, and support community make it a compelling choice for clinical trial data analysis.

As it stands, SAS remains the most widely used software in big-pharma for clinical trial data analysis. Stata however offers distinct advantages in terms of user-friendliness, tailored statistical functionalities, advanced graphics, and a supportive user community. Consider adopting Stata to streamline your clinical trial analyses and unlock its vast potential for gaining insights from research outcomes. An in-depth overview of Stata 18 can be found here. A summary of it’s features for biostatisticians can be found here.

Further reading:

Using Stata for Handling CDISC Complient Data Sets and Outputs (lexjansen.com)

P Values, Confidence Intervals and Clinical Trials

P values are so ubiquitous in clinical research that it’s easy to take for granted that they are being understood and interpreted correctly. After-all, one might say, they are just simple proportions and it’s not brain surgery. At times, however, its’ the simplest of things that are easiest to overlook. In fact, the definitions and interpretations of p values are sufficiently subtle that even a minute pivot from an exact definition can lead to interpretations that are wildly misleading.

In the case of clinical trials, p values have a momentous impact on decision making in terms of whether or not to pursue and invest further into the development and marketing of a given therapeutic. In the context of clinical practice p values drive treatment decisions for patients as they essentially comprise the foundational evidence upon which these treatment decisions are made. This is perhaps as it should be, as long as the definition of p values and their interpretations are sound.

A counter-point to this is the bias towards publishing only studies with a statistically significant p value, as well as the fact that many studies are not sufficiently reproducible or reproduced. This leaves clinicians with an impression that evidence for a given treatment is stronger than the full picture would suggest. This however is a publishing issue rather than an issue of significance tests themselves. This article focusses on interpretation issues only.

As p values apply to the interpretation of both parametric and non-parametric tests in much the same way, this article will focus on parametric examples.

Interpreting p values in superiority/difference study designs

This refers to studies where we are seeking to find a difference between two treatment groups or between a single group measured at two time points. In this case the null hypothesis is that there is no difference between the two treatment groups or no effect of the treatment, as the case may be.

According to the significance testing framework all p values are calculated based upon an assumption that the null hypothesis is true. If a study yields a p value of 0.05, this means that we would expect to see a difference between the two groups at least as extreme as the observed effect 5% of the time; if the study were to be repeated. In other words, if there is no true difference between the two treatment groups and we ran the experiment 20 times on 20 independent samples from the same population, we would expect to see a result this extreme once out of the 20 times.

This of course is not a very helpful way of looking at things if our goal is to make a statement about treatment effectiveness. The inverse likely makes more intuitive sense: if were were to run this study 20 times on distinct patient samples from the same population, 19 out of 20 times we would not expect a result this extreme if there was no true effect. Based on the rarity of the observed effect, we conclude that likelihood of the null hypothesis being the optimal explanation of the data is sufficiently low that we can reject it. Thus our alternative research hypothesis, that there is a difference between the two treatments, is likely to be true. As the p value does not tell us whether the difference is a positive or negative direction, care should of course be taken to confirm which of the treatments holds the advantage.

P values in non-inferiority or equivalence studies.

In non-inferiority and equivalence studies a non-statistically significant p value can be a welcome result, as can a very low p value where the differences were not clinically significant, or where the new treatment is shown to be superior to the standard treatment. By only requiring the treatment not to be inferior, more power is retained and a smaller sample size can be used.

The interpretation of the p value is much the same as for superiority studies, however the implications are different. In these types of studies it is ideal for the confidence intervals for the individual treatment effects to be narrow as this provides certainty that the estimates obtained are accurate in the absence of a statistically significant difference between the two estimates.

While alternatives to p values exist, such as Bayesian statistics, these statistics have limitations of their own and are subject to the same propensity for misuse and misinterpretation as frequentist statistics are. Thus it remains important to take caution in interpreting all statistical results.

What p values do not tell you

A p value of 0.05 is not the same as saying that there is only a 5% chance that the treatment wont work. Whether or not the treatment works in the individual is another probability entirely. It is also not the same as saying there is a 5% chance of the null hypothesis being true. The p value is a statistic that is based on the assumption that the null hypothesis is true and on that basis gives the likelihood of the observed result.

Nor does the p value represent the chance of making a type 1 error. As each repetition of the same experiment produces a different p value, it does not make sense to characterise the p value as the chance of incorrectly rejecting the null hypothesis ie making a type one error. Instead, an alpha cut-off point of 0.05 should be seen as indicating a result rare enough under the null hypothesis that we are now willing to reject the null as the most likely explanation given the data. Under a type-one error alpha of 0.05 this decision is expected to be wrong 5% of the time, regardless of the p value achieved in the statistical test. The relationship between the critical alpha and statistical power is illustrated below.

Another misconception is that a small p value provides strong support for a given research hypothesis. In reality a small p value does not necessarily translate to a big effect, nor a clinically meaningful one. The p value indicates a statistically significant result, however it says nothing about the magnitude of the effect or whether this result is clinically meaningful in the context of the study. A p value of 0.00001 may appear to be a very satisfactory result, however if the difference observed between the two groups is very small then this is not always the case. All it would be saying is that “we are really really sure that there is only minimal difference between the two treatments”, which in a superiority design may not be as desired.

Minimally important difference (MID)

This is where the importance of pre-defining a minimally important difference (MID) becomes evident. The MID, or clinically meaningful difference. should be defined and quantified in the design stage before the study is to be undertaken. In the case of clinical studies this should generally be done in consultation with the clinician or disease expert concerned.

The MID may take different forms depending on whether a study is a superiority design, versus an equivalence or non-inferiority design. In the case of a superiority design or where the goal of the study is to detect a difference, the MID is the threshold of minimum difference at which we would be willing to consider the new treatment worth pursuing over the standard treatment or control being used as the comparator. In the case of a non-inferiority design the MID would be the minimum lower threshold at which we would still consider the new treatment as equally effective or useful as the standard treatment. Equivalence design on the other hand may sometimes rely on an interval around the standard treatment effect.

When interpreting results of clinical studies it is of primary importance to keep a clinically meaningful difference in mind, rather than defaulting to the p value in isolation. In cases where the p value is statistically significant, it is important to ask whether the difference between comparison groups is also as large as the MID or larger.

Confidence Intervals

All statistical tests that involve p values can produce a corresponding confidence interval for the estimates. Unlike p values, confidence intervals do not rely on an assumption of the null hypothesis but rather on the assumption that the sample approximates the population of interest. A common estimate in clinical trials where confidence intervals become important is the treatment effect. Very often this translates to the difference in means of a surrogate endpoint between two groups, however confidence intervals are also important to consider for individual group means/ treatment effects, which are an estimate of the population means of the endpoint in these distinct groups/treatment categories.

Confidence interval for the mean

A 95% confidence interval of the estimate of the mean indicates that, if this study were to be repeated, the mean value is expected to fall within this interval 95% of the time. While this estimate is based on the real mean of the study sample our interest remains in making inferences about the wider population who might later be subject to this treatment. Thus inferentially the observed mean and it’s confidence interval are both considered an estimate of the population values.

In a nutshell the confidence interval indicates how sure we can be of the accuracy of the estimate. A narrower interval indicates greater confidence and a wider interval less. The p value of the estimate indicates how certain we can be of this result, ie the interval itself.

Confidence interval for the mean difference, treatment effects or difference in treatment effects

The mean difference in treatment effect between two groups is an important estimate in any comparison study, from superiority to non-inferiority clinical trial designs. Treatment response is mainly ascertained from repeated measures of surrogate endpoint data on the individual level. One form of mean difference is repeated measures data from the same individuals at different time points, these individuals’ differences could then be compared between two independent treatment groups. In the context of clinical trials, confidence intervals of the mean difference can relate to an individual’s treatment effect or to group differences in treatment effects.

A 95% Confidence interval of the mean difference in treatment effect indicates that 95 per cent of the time, if this study were to be repeated, the true difference in treatment effect between the groups is expected to fall within this interval. A confidence interval containing zero indicates that a statistically significant difference between the two groups has not been found. Namely, if part of the time the true population value representing the difference is expected to fall above zero on the number line and part of the time to fall below zero, indicating a difference in the opposite direction, we cannot be sure whether one group is higher or lower than the other.

Much ho-hum has been made of p values in recent years but they are here to stay. While alternatives to p values exist, such as Bayesian methods, these statistics have limitations of their own and are subject to the same propensity for misuse and misinterpretation as frequentist statistics are. Thus it remains important to take caution in interpreting all statistical results.

Sources and further reading:

Gao, P-Values – A chronic conundrum, BMC Medical Research Methodology (2020), 20:167
https://doi.org/10.1186/s12874-020-01051-6

The Royal College of Ophthalmologists, The clinician’s guide to p values, confidence intervals, and magnitude of effects, Eye (2022) 36:341–342; https://doi.org/10.1038/s41433-021-01863-w

The role of Biostatisticians, Bioinformaticians & other Data Experts in Clinical Research

As a medical researcher or a small enterprise in the life sciences industry, you are likely to encounter many experts using statistical and computational techniques to study biological, clinical and other health data. These experts can come from a variety of fields such as biostatistics, bioinformatics, biometrics, clinical data science and epidemiology. Although these fields do overlap in certain ways they differ in purpose, focus, and application. All four areas listed above focus on analysing and interpreting either biological, clinical data or public health data but they typically do so in different ways and with different goals in mind. Understanding these differences can help you choose the most appropriate specialists for your research project and get the most out of their expertise. This article will begin with a brief description of these disciplines for the sake of disambiguation, then focus on biostatistics and bioinformatics, with a particular overview of the roles of biostatisticians and bioinformatics scientists in clinical trials.

Biostatisticians

Biostatisticians use advanced biostatistical methods to design and analyse pre-clinical experiments, clinical trials, and observational studies predominantly in the medical and health sciences. They can also work in ecological or biological fields which will not be the focus of this article. Biostatisticians tend to work on varied data sets, including a combination of medical, public health and genetic data in the context of clinical studies. Biostatisticians are involved in every stage of a research project, from planning and designing the study, to collecting and analysing the data, to interpreting and communicating the results. They may also be involved in developing new statistical methods and software tools. In the UK the term “medical statistician” has been in common use over the past 40 years to describe a biostatistician, particularly one working in clinical trials, but it is becoming less used due to the global nature of the life sciences industry.

Bioinformaticians

Bioinformaticians use computational and statistical techniques to analyse and interpret large datasets in the life sciences. They often work with multi-omics data such as genomics, proteomics transcriptomics data and use tools such as large databases, algorithms, and specialised software programs to analyse and make sense of sequencing and other data. Bioinformaticians develop analysis pipelines and fine-tune methods and tools for analysing biological data to fit the evolving needs of researchers.

Clinical data scientists

Data scientists use statistical and computational modelling methods to make predictions and extract insights from a wide range of data. Often, data is real-world big data of which it might not be practical to analyse using other methods. In a clinical development context data sources could include medical records, epidemiological or public health data, prior clinical study data, or IOT and IOB sensor data. Data scientists may combine data from multiple sources and types. Using analysis pipelines, machine learning techniques, neural networks, and decision tree analysis this data can be made sense of. The better the quality of the input data the more precise and accurate any predictive algorithms can be.

Statistical programmers

Statistical programmers help statisticians to efficiently clean and prepare data sets and mock TFLs in preparation for analysis. They set up SDTM and ADaM data structures in preparation for clinical studies. Quality control of data and advanced macros for database management are also key skills.

Biometricians

Biometricians use statistical methods to analyse data related to the characteristics of living organisms. They may work on topics such as growth patterns, reproductive success, or the genetic basis of traits. Biometricians may also be involved in developing new statistical methods for analysing data in these areas. Some use the terms biostatistician and biometrician interchangeably however for the purpose of this article they remain distinct.

Epidemiologists

Epidemiologists study the distribution and determinants of diseases in populations. Using descriptive, analytical, or experimental techniques, such as cohort or case-control studies, they identify risk factors for diseases, evaluate the effectiveness of public health interventions, as well as track or model the spread of infectious diseases. Epidemiologists use data from laboratory testing, field studies, and publicly available health data. They can be involved in developing new public health policies and interventions to prevent or control the spread of diseases.

Clinical trials and the role of data experts

Clinical trials involve testing new treatments, interventions, or diagnostic tests in humans. These studies are an important step in the process of developing new medical therapies and understanding the effectiveness and safety of existing treatments.

Biostatisticians are crucial to the proper design and analysis of clinical trials. So that optimal study design can take place, they may first have to conduct extensive meta-analysis of previous clinical studies and RWE generation based on available real-world data sets or R&D results. They may also be responsible for managing the data and ensuring its quality, as well as interpreting and communicating the results of the trial. From developing the statistical analysis plan and contributing to the study protocol, to final analysis and reporting, biostatisticians have a role to play across the project time-line.

During a clinical trial, statistical programmers may prepare data sets to CDISC standards and pre-specified study requirements, maintain the database, as well as develop and implement standard SAS code and algorithms used to describe and analyse the study data.

Bioinformaticians may be involved in the design and analysis stages of clinical trials, particularly if the trial design involves the use of large data sets such as sequencing data for multi-omics analysis. They may be responsible for managing and analysing this data, as well as developing software tools and algorithms to support the analysis.

Data scientists may be involved in designing and analysing clinical trials at the planning stage, as well as in developing new tools and methods. The knowledge gleaned from data science models can be used to improve decision-making across various contexts, including life sciences R&D and clinical trials. Some applications include optimising the patient populations used in clinical trials; feasibility analysis using simulation of site performance, region, recruitment and other variables, to evaluate the impacts of different scenarios on project cost and timeline.

Biometricians and epidemiologists may also contribute to clinical trials, particularly if the trial is focused on a specific population or on understanding the factors that influence the incidence or severity of a disease. They may contribute to the design of the study, collecting and analysing the data, or interpreting the results.

Overall, the role of these experts in clinical trials is to use their varied expertise in statistical analysis, data management, and research design to help understand the safety and effectiveness of new treatments and interventions.

The role of biostatistician in clinical trials

Biostatisticians may be responsible for developing the study protocol, determining the sample size, producing the randomisation schedule, and selecting the appropriate statistical methods for analysing the data. They may also be responsible for managing the data and ensuring its quality, as well as interpreting and communicating the results of the trial.

SDTM data preparation

The Study Data Tabulation Model (SDTM) is a data standard that is used to structure and organize clinical study data in a standardized way. Depending on how a CRO is structured, either biostatisticians, statistical programmers, or both will be involved in mapping the data collected in a clinical trial to the SDTM data set, which involves defining the structure and format of the data and ensuring that it is consistent with the standard. This helps to ensure that the data is organised in a way that is universally interpretable. This process involves working with the research team to ensure the appropriate variables and categories are defined before reviewing and verifying the data to ensure that it is accurate, complete and in line with industry standards. Typically the SDTM data set will be established early at the protocol phase and populated later once trial data is accumulated.

Creating and analysing the ADaM dataset

In clinical trials, the Analysis Data Model (ADaM) is a data set model used to structure and organize clinical trial data in a standardized way for the purpose of statistical analysis. ADaM data sets are used to store the data that will be analysed as part of the clinical trial, and are typically created from the Study Data Tabulation Model (SDTM) data sets, which contain the raw data collected during the trial. This helps to ensure the reliability and integrity of the data, and makes it easier to analyse and interpret the results of the trial.

Biostatisticians and statistical programmers are responsible for developing ADaM data sets from the SDTM data, which involves selecting the relevant variables and organizing them in a way that is appropriate for the particular statistical analyses that will be conducted. While statistical programmers may create derived variables, produce summary statistics, TFLs, and organise the data into appropriate datasets and domains, biostatisticians are responsible for conducting detailed statistical analyses of the data and interpreting the results. This may include tasks such as testing hypotheses, identifying patterns and trends in the data, and developing statistical models to understand the relationships between the data and the research questions the trial seeks to answer.

The role of biostatisticians, specifically, in developing ADaM data sets from SDTM data is to use their expertise in statistical analysis and research design to guide statistical programmers in ensuring that the data is organised, structured, and formatted in a way that is appropriate for the analyses that will be conducted, and to help understand and interpret the results of the trial.

A Biostatistician’s role in study design & planning

Biostatisticians play a critical role in the design, analysis, and interpretation of clinical trials. The role of the biostatistician in a clinical trial is to use their expertise in statistical analysis and research design to help ensure that the trial is conducted in a scientifically rigorous and unbiased way, and to help understand and interpret the results of the trial. Here is a general overview of the tasks that a biostatistician might be involved in during the different stages of a clinical trial:

Clinical trial design: Biostatisticians may be involved in designing the clinical trial, including determining the study objectives, selecting the appropriate study population, and developing the study protocol. They are responsible for determining the sample size and selecting the appropriate statistical methods for analysing the data. Often in order to carry out these tasks, preparatory analysis will be necessary in the form of detailed meta-analysis or systematic review.

Sample size calculation: Biostatisticians are responsible for determining the required sample size for the clinical trial. This is an important step, as the sample size needs to be large enough to detect a statistically significant difference between the treatment and control groups, but not so large that the trial becomes unnecessarily expensive or time-consuming. Biostatisticians use statistical algorithms to determine the sample size based on the expected effect size, the desired level of precision, and the expected variability of the data. This information is informed by expert opinion and simulation of the data from previous comparable studies.

Randomisation schedules: Biostatisticians develop the randomisation schedule for the clinical trial, which is a plan for assigning subjects to the treatment and control groups in a random and unbiased way. This helps to ensure that the treatment and control groups are similar in terms of their characteristics, which helps to reduce bias or control for confounding factors that might affect the results of the trial.

Protocol development: Biostatisticians are involved in developing the statistical and methodological sections of the clinical trial protocol, which is a detailed plan that outlines the objectives, methods, and procedures of the study. In addition to outlining key research questions and operational procedures the protocol should include information on the study population, the interventions being tested, the outcome measures, and the data collection and analysis methods.

Data analysis: Biostatisticians are responsible for analysing the data from the clinical trial, including conducting interim analyses and making any necessary adjustments to the protocol. They play a crucial role in interpreting the results of the analysis and communicating the findings to the research team and other stakeholders.

Final analysis and reporting: Biostatisticians are responsible for conducting the final analysis of the data and preparing the final report of the clinical trial. This includes summarising the results, discussing the implications of the findings, and making recommendations for future research.

The role of bioinformatician in biomarker-guided clinical studies.

Biomarkers are biological characteristics that can be measured and used to predict the likelihood of a particular outcome, such as the response to a particular treatment. Biomarker-guided clinical trials use biomarkers as a key aspect of the study design and analysis. In biomarker-guided clinical trials where the biomarker is based on genomic sequence data, bioinformaticians may play a particularly important role in managing and analysing the data. Genomic and other omics data is often large and complex, and requires specialised software tools and algorithms to analyse and interpret. Bioinformaticians develop and implement these tools and algorithms, as well as for managing and analysing the data to identify patterns and relationships relevant to the trial. Bioinformaticians use their expertise in computational biology to to help understand the relationship between multi-omics data and the outcome of the trial, and to identify potential biomarkers that can be used to guide treatment decisions.

Processing sequencing data is a key skill of bioinformaticians that involves several steps, which may vary depending on the specific goals of the analysis and the type of data being processed. Here is a general overview of the steps that a bioinformatician might take to process sequencing data:

  1. Data pre-processing: Cleaning and formatting the data so that it is ready for analysis. This may include filtering out low-quality data, correcting errors, and standardizing the format of the data.
  2. Mapping: Aligning the sequenced reads to a reference genome or transcriptome in order to determine their genomic location. This can be done using specialized software tools such as Bowtie or BWA.
  3. Quality control: Checking the quality of the data and the alignment, and identifying and correcting any problems that may have occurred during the sequencing or mapping process. This may involve identifying and removing duplicate reads, or identifying and correcting errors in the data.
  4. Data analysis: Using statistical and computational techniques to identify patterns and relationships in the data such as identifying genetic variants, analysing gene expression levels, or identifying pathways or networks that are relevant to the study.
  5. Data visualization: Creating graphs, plots, and other visualizations to help understand and communicate the results of the analysis.

Once omics data has been analysed, the insights obtained can be used for tailoring therapeutic products to patient populations in a personalised medicine approach.

A changing role of data experts in life sciences R&D and clinical research

Due to the need for better therapies and health solutions, researchers are currently defining diseases at more granular levels using multi-omics insights from DNA sequencing data which allows differentiation between patients in the biomolecular presentation of their disease, demographic factors, and their response to treatment. As more and more of the resulting therapies reach the market the health care industry will need to catch up in order to provide these new treatment options to patients.

Even after a product receives regulatory approval, payers can opt not to reimburse patients, so financial benefit should be demonstrated in advance where possible. Patient reported outcomes and other health outcomes are becoming important sources of data to consider in evidence generation. Evidence provided to payers should aim to demonstrate financial as well as clinical benefit of the product.

In this context, regulators are becoming aware of the need for innovation in developing new ways of collecting treatment efficacy and other data used to assess novel products for regulatory approval. The value of observational studies and real-world-data sources as a supplement clinical trial data is being acknowledged as a legitimate and sometimes necessary part of the product approval process. Large scale digitisation now makes it easier to collect patient-centric data directly from clinical trial participants and users via devices and apps. Establishing clear evidence expectations from regulatory agencies then Collaborating with external stakeholders, data product experts, and service-providers to help build new evidence-building approaches.

Expert data governance and quality control is crucial to the success of any new methods to be implemented analytically. Data from different sources, such as IOT sensor data, electronic health records, sequencing data for multi-omics analysis, and other large data sets, has to be combined cautiously and with robust expert standards in place.

From biostatistics, bioinformatics, data science, CAS, and epidemiology for public heath or post-market modelling; a bespoke team of integrated data and analytics specialists is now as important to a product development project as the product itself to gaining competitiveness and therefore success in the marketplace. Such a team should be applying a combination of established data collection methodologies eg. clinical trials and systematic review, and innovative methods such as machine learning models that draw upon a variety of real world data sources to find a balance between advancing important innovation and mitigating risk.

Sex Differences in Clinical Trial Recruiting

The following article investigates several systematic reviews into sex and gender representation in individual clinical trial patient populations. In these studies sex ratios are assessed and evaluated by various factors such as clinical trial phase, disease type under investigation and disease burden in the population. Sex differences in the reporting of safety and efficacy outcomes are also investigated. In many cases safety and efficacy outcomes are pooled, rather than reported individually for each sex, which can be problematic when findings are generalised to the wider population. In order to get the dosage right for different body compositions and avoid unforeseen outcomes in off label use or when a novel therapeutic first reaches the market, it is important to report sex differences in clinical trials. Due to the unique nuances of disease types and clinical trial phases it is important to realise that a 50-50 ratio of male to female is not always the ideal or even appropriate in every clinical study design. Having the right sex balance in your clinical trial population will improve the efficiency and cost-effectiveness of your study. Based upon the collective findings a set of principles are put forth to guide the researcher in determining the appropriate sex ratio for their clinical trial design.

Sex difference by clinical trial phase

  • variation in sex enrolment ratios for clinical trial phases
  • females less likely to participate in early phases, due to increased risk of adverse events
  • under-representation of women in phase III when looking at disease prevalence

It has been argued that female representation in clinical trials is lacking, despite recent efforts to mitigate the gap. US data from 2000-2020 suggests that trial phase has the greatest variation in enrolment when compared to other factors, with median female enrolment being 42.9%, 44.8%, 51.7%, and 51.1% for phases I, I/II to II, II/III to III, and IV4. This shows that median female enrolment gradually increases as trials progress, with the difference in female enrolment between the final phases II/III to III and IV being <1%. Additional US data on FDA approved drugs including trials from as early as 1993 report that female participation in clinical trials is 22%, 48%, and 49% for trial phases I, II, and III respectively2. While the numbers for participating sexes are almost equal in phases II and III, women make up only approximately one fifth of phase I trial populations in this dataset2. The difference in reported participation for phase I trials between the datasets could be due to an increase in female participation in more recent years. The aim of a phase I trial is to evaluate safety and dosage, so it comes as no surprise that women, especially those of childbearing age, are often excluded due to potential risks posed to foetal development.

In theory, women can be included to a greater extent as trial phases progress and the potential risk of severe adverse events decreases. By the time a trial reaches phase III, it should ideally reflect the real-world disease population as much as possible. European data for phase III trials from 2011-2015 report 41% of participants being female1, which is slightly lower than female enrolment in US based trials. 26% of FDA approved drugs have a >20% difference between the proportion of women in phase II & III clinical trials and the prevalence of women in the US with the disease2, and only one of these drugs shows an over-representation of women.

Reporting of safety and efficacy by sex difference

  • Both safety and efficacy results tend to differ by sex.
  • Reporting these differences is inconsistent and often absent
  • Higher rates of adverse events in women are possibly caused by less involvement or non stratification in dose finding and safety studies.
  • There is a need to enforce analysis and reporting of sex differences in safety and efficacy data

Sex differences in response to treatment regarding both efficacy and safety have been widely reported. Gender subgroup analyses regarding efficacy can reveal whether a drug is more or less effective in one sex than the other. Gender subgroup analyses for efficacy are available for 71% of FDA approved drugs, and of these 11% were found to be more efficacious in men and 7% in women2. Alternatively, only 2 of 22 European Medicines Agency approved drugs examined were found to have efficacy differences between the sexes1. Nonetheless, it is important to study the efficacy of a new drug on all potential population subgroups that may end up taking that drug.

The safety of a treatment also differs between the sexes, with women having a slightly higher percentage (p<0.001) of reported adverse events (AE) than men for both treatment and placebo groups in clinical trials1. Gender subgroup analyses regarding safety can offer insights into the potential risks that women are subjected to during treatment. Despite this, gender specific safety analyses are available for only 45% of FDA approved drugs, with 53% of these reporting more side effects in women2. On average, women are at a 34% increased risk of severe toxicity for each cancer treatment domain, with the greatest increased risk being for immunotherapy (66%). Moreover, the risk of AE is greater in women across all AE types, including patient-reported symptomatic (female 33.3%, male 27.9%), haematologic (female 45.2%, male 39.1%) and objective non-haematologic (female 30.9%, male 29.0%)3. These findings highlight the importance of gender specific safety analyses and the fact that more gender subgroup safety reporting is needed. More reporting will increase our understanding of sex-related AE and could potentially allow for sex-specific interventions in the future.

Sex differences by disease type and burden

  • Several disease categories have recently been associated with lower female enrolment
  • Men are under-represented as often as women when comparing enrolment to disease burden proportions
  • There is a need for trial participants to be recruited on a case-by-case basis, depending on the disease.

Sex differences by disease type

When broken down by disease type, the sex ratio of clinical trial participation shows a more nuanced picture. Several disease categories have recently been associated with lower female enrolment, compared to other factors including trial phase, funding, blinding, etc4. Women comprised the smallest proportions of participants in US-based trials between 2000-2020 for cardiology (41.4%), sex-non-specific nephrology and genitourinary (41.7%), and haematology (41.7%) clinical trials4. Despite women being

proportionately represented in European phase III clinical studies between 2011-2015 for depression, epilepsy, thrombosis, and diabetes, they were significantly under-represented for hepatitis C, HIV, schizophrenia, hypercholesterolaemia, and heart failure and were not found to be overrepresented in trials for any of the disease categories examined1. This shows that the gap in gender representation exists even in later clinical trial phases when surveying disease prevalence, albeit to a lesser extent. Examining disease burden shows that the gap is even bigger than anticipated and includes the under-representation of both sexes.

Sex Differences by Disease Burden

It is not until the burden of disease is considered that men are shown to be under-represented as often as women. Including burden of disease can depict proportionality relative to the variety of disease manifestations between men and women. It can be measured as disability-adjusted life years (DALYs), which represent the number of healthy years of life lost due to the disease. Despite the sexes each making up approximately half of clinical trial participants overall in US-based trials between 2000-2020, all disease categories showed an under-representation of either women or men relative to disease burden, except for infectious disease and dermatologic clinical trials4. Women were under-represented in 7 of 17 disease categories, with the greatest under-representation being in oncology trials, where the difference between the number of female trial participants and corresponding DALYs is 3.6%. Men were under-represented compared with their disease burden in 8 of 17 disease categories, with the greatest difference being 11.3% for musculoskeletal disease and trauma trials.4 Men were found to be under-represented to a similar extent to women, suggesting that the under-representation of either sex could be by coincidence. Alternatively, male under-representation could potentially be due to the assumption of female under-representation leading to overcorrection in the opposite direction. It should be noted that these findings would benefit from statistical validation, although they illustrate the need for clinical trial participants to be recruited on a case-by-case basis, depending on the disease.

Takeaways to improve your patient sample in clinical trial recruiting:

  1. Know the disease burden/DALYs of your demographics for that disease.
  2. Try to balance the ratio of disease burden to the appropriate demographics for your disease
  3. Aim to recruit patients based on these proportions
  4. Stratify clinical trial data by the relevant demographics in your analysis. For example: toxicity, efficacy, adverse events etc should always be analyses separately for male and female to come up wit the respective estimates.
  5. Efficacy /toxicity etc should always be reported separately for male and female. reporting difference by ethnicity is also important as many diseases differentially affect certain ethnicity and the corresponding therapeutics can show differing degrees of efficacy and adverse events.

The end goal of these is that medication can be more personalised and any treatment given is more likely to help and less likely to harm the individual patient.

Conclusions

There is room for improvement in the proportional representation of both sexes in clinical trials and knowing a disease demographic is vital to planning a representative trial. Assuming the under-representation is on the side of female rather than male may lead to incorrect conclusions and actions to redress the balance. Taking demographic differences in disease burden into account when recruiting trial participants is needed. Trial populations that more accurately depict the real-world populations will allow a therapeutic to be tailored to the patient.

Efficacy and safety findings highlight the need for clinical study data to be stratified by sex, so that respective estimates can be determined. This enables more accurate, sex/age appropriate dosing that will maximise treatment efficacy and patient safety, as well as minimise the chance of adverse events. This also reduces the risks associated with later off label use of drugs and may avoid modern day tragedies resembling the thalidomide tragedy. Moreover, efficacy and adverse events should always be reported separately for men and women, as the evidence shows their distinct differences in response to therapeutics.

See our full report on diversity in patient recruiting for clinical trials.

References:

1. Dekker M, de Vries S, Versantvoort C, Drost-van Velze E, Bhatt M, van Meer P et al. Sex Proportionality in Pre-clinical and Clinical Trials: An Evaluation of 22 Marketing Authorization Application Dossiers Submitted to the European Medicines Agency. Frontiers in Medicine. 2021;8.

2. Labots G, Jones A, de Visser S, Rissmann R, Burggraaf J. Gender differences in clinical registration trials: is there a real problem?. British Journal of Clinical Pharmacology. 2018;84(4):700-707.

3. Unger J, Vaidya R, Albain K, LeBlanc M, Minasian L, Gotay C et al. Sex Differences in Risk of Severe Adverse Events in Patients Receiving Immunotherapy, Targeted Therapy, or Chemotherapy in Cancer Clinical Trials. Journal of Clinical Oncology. 2022;40(13):1474-1486.

4. Steinberg J, Turner B, Weeks B, Magnani C, Wong B, Rodriguez F et al. Analysis of Female Enrollment and Participant Sex by Burden of Disease in US Clinical Trials Between 2000 and 2020. JAMA Network Open. 2021;4(6):e2113749.

Latent Variable Modelling And The Chi Squared Exact Fit Statistic

Latent variable modelling and the chi squared exact fit statistic

Latent variable models are exploratory statistical models used extensively throughout clinical and experimental research in medicine and the life sciences in general. Psychology and neuroscience are two key sub-disciplines where latent variable models are routinely employed to answer a myriad of research questions from the impact of personality traits on success metrics in the workplace (1) to measuring inter-correlated activity of neural populations in the human brain based on neuro-imaging data (2). Through latent variable modelling, dispositions, states or process which must be inferred rather than directly measured can be linked causally to more concrete measurements.
Latent variable models are exploratory or confirmatory in nature in the sense that they are designed to uncover causal relationships between observable or manifest variables and corresponding latent variables in an inter-correlated data set. They use structural equation modelling (SEM) and more specifically factor analysis techniques to determine these causal relationships which and allow the testing of numerous multivariate hypotheses simultaneously. A key assumption of SEM is that the model is fully correctly specified. The reason for this is this is that one small misspecification can affect all parameter estimations in the model, rendering inaccurate approximations which can combine in unpredictable ways (3).

With any postulated statistical model it is imperative to assess and validate the model fit before concluding in favour of the integrity of the model and interpreting results. The acceptable way to do this across all structural equation models is the chi squared (χ²) statistic.

A statistically significant χ² statistic is indicative of the following:

  • A systematically miss-specified model with the degree of misspecification a function of the χ² value.
  • The set of parameters specified in the model do not adequately fit the data and thus that the parameter estimates of the model are inaccurate. As χ² operates on the same statistical principles as the parameter estimation, it follows that in order to trust the parameter estimates of the model we must also trust the χ², or vice versa.
  •  As a consequence there is a need for an investigation of where these misspecification have occurred and a potential readjustment of the model to improve its accuracy.

While one or more incorrect hypotheses may have caused the model misspecification, the misspecification could equally have resulted from other causes. It is important to thus investigate the causes of a significant model fit test . In order to properly do this the following should be evaluated:

  • Heterogeneity:
  •  Does the causal model vary between sub groups of subjects?
  • Are there any intervening within subject variables?
  • Independence:
  • Are the observations truly independent?
  • Latent variable models involve two key assumptions: that all manifest variables are independent after controlling for any latent variables and, an individual’s position on a manifest variable is the result of that individual’s position on the corresponding latent variable (3).
  • Multivariate normality:
  • Is the multivariate normality assumption satisfied?


The study:

A 2015 meta-analysis of 75 latent variable studies drawn from 11 psychology journals has highlighted a tendency in clinical researchers to ignore the χ² exact fit statistic when reporting and interpreting the results of the statistical analysis of latent variable models (4).
97% of papers reported at least one appropriate model, despite the fact that 80% of these did not pass the criteria for model fit and the χ² exact fit statistic was ignored. Only 2% of overall studies concluded that the model doesn’t fit at all and one of these interpreted a model anyway (4).
Reasons for ignoring the model fit statistic: overly sensitive to sample size, penalises models when number of variables is high, general objection to the logic of exact fit hypothesis. Overall broach consensus of preference for Approximate fit indices (AFI).
AFI are instead applied in these papers to justify the models. This typically leads to questionable conclusions. In all just 41% of studies reported χ² model fit results. 40% of the studies that failed to report a p value for the reported χ² value did report a degrees of freedom. When this degrees of freedom was used to cross check the unreported p values, all non-reported p values were in fact significant.
The model fit function was usually generated through maximum likelihood methods, however 43% of studies failed to report which fit function was used.
A further tendency to accept the approximate fit hypothesis when in fact there was no or little evidence of approximate fit. This lack of thorough model examination empirical evidence of questionable validity. 30% of studies showed custom selection of more lax cut-off criteria for the approximate fit statistics than was conventionally acceptable, while 53% failed to report on cut-off criteria at all.
Assumption testing for univariate normality was assessed in only 24% of studies (4).
Further explanation of  χ² and model fit:

The larger the data set the more that increasingly trivial discrepancies are detected as a source of model misspecification. This does not mean that trivial discrepancies become more important to the model fit calculation, it means that the level of certainty with which these discrepancies can be considered important has increased. In other words, the statistical power has increased. Model misspecification can be the result of both theoretically relevant and irrelevant/peripheral causal factors which both need to be equally addressed. A significant model fit statistic indicating model misspecification is not trivial just because the causes of the misspecification are trivial. It is instead the case that trivial causes are having a significant effect and thus there is a significant need for them to be addressed. The χ² model fit test is the most sensitive way to detect misspecification in latent variable models and should be adhered to above other methods even when sample size is high. In the structural equation modelling context of multiple hypotheses, a rejection of model fit does not result in the necessary rejection of each of the models hypotheses (4).
Problems with AFI:

The AFI statistic does provide a conceptually heterogeneous set of fit indices for each hypothesis, however none of these indices are accompanied by a critical value or significance level and all except one arise from unknown distributions. The fit indices are a function of χ² but unlike the χ²  fit statistic they do not have a verified statistical basis nor do they present a statistically rigorous test of model fit. Despite this satisfactory AFI values across hypotheses are being used to justify the invalidity of a significant χ² test.
Mote Carlo simulations of AFI concluded that it is not possible to determine universal cut off criteria in any forms of model tested.  Using AFI, the probability of correctly rejecting a mis-specified model decreased with increasing sample size. This is the inverse of the  statistic. Another problem with AFI compared to χ²  is that the more severe the model misspecification or correlated errors, the more unpredictable the AFI become. Again this is the inverse of what happens with the χ²  statistic (4).
The take away:

Based on the meta-analysis the following best practice principles are recommended in addition to adequate attention to the statistical assumptions of heterogeneity, independence and multivariate normality outlined above:

  1. Pay attention to distributional assumptions.
  2. Have a theoretical justification for your model.
  3. Avoid post hoc model modifications such as dropping indicators, allowing cross-loadings and correlated error terms.
  4. Avoid confirmation bias.
  5. Use an adequate estimation method.
  6. Recognise the existence of equivalence models.
  7. Justify causal inferences.
  8. Use clear reporting that is not selective.

Image:  

Michael Eid, Tanja Kutscher,  Stability of Happiness, 2014 Chapter 13 – Statistical Models for Analyzing Stability and Change in Happiness
​https://www.sciencedirect.com/science/article/pii/B9780124114784000138

​References:
(1). Latent Variables in Psychology and the Social Sciences

(2) Structural equation modelling and its application to network analysis in functional brain imaging
https://onlinelibrary.wiley.com/doi/abs/10.1002/hbm.460020104

(3) Chapter 7: Assumptions in Structural Equation modelling
https://psycnet.apa.org/record/2012-16551-007

(4) A cautionary note on testing latent variable models
https://www.frontiersin.org/articles/10.3389/fpsyg.2015.01715/full