Estimands & Estimation Within Clinical Trials


Accessible statistical methods to determine treatments effects that matter to patients in randomised controlled trials

Team: Suzie Cro, Victoria Cornelius, Ian White, James Carpenter


The calculation of different types of treatment effects, including those that are more relevant for patients, has recently been brought to the forefront with the publication of an addendum to international drug trial guidelines ( ICH E9 (R1) - addendum on estimands and sensitivity analysis in clinical trials to the guideline on statistical principles for clinical trials). However, the guidance does not provide statistical methods for achieving this. Whilst some statistical methods have been proposed for calculating more patient centred effects, these are limited and not widely used.


We are conducting a programme of research to develop and evaluate accessible statistical methods to estimate treatment effects in trials that are of greater relevance patients, such as the effect of treatment if taken as intended. Alongside statistical methods development, we are working with public partners to improve the communication of statistical information from trials, to enable both more relevant and understandable information. 


How should compliance be defined in smartphone app trials?

Team: Jack Elkes, Suzie Cro, Victoria Cornelius

The need to validate the use of smartphone apps and other digital technologies in healthcare is rapidly growing. A randomised controlled trial remains the gold standard approach and typically, an intention-to-treat analysis will be performed to determine if the intervention is beneficial.

However, the use of an app is known to decline substantially over time and an additional question of interest to answer is how effective the app in those is who use it (‘complie’).  Unlike drug and behavioural interventions, compliance with digital interventions is more complex to define. There are currently recommended approaches to define participant compliance for smartphone app use in a trial. This is needed when calculating the benefit of treatment receipt (using complier causal inference methods).

We are conducting research to identify the different ways patients access the app based on key metrics; duration in app, pages accessed, and time of day accessed. PCA will be used to identify clusters of the different user profiles, which in turn will help us to develop a strategy for defining compliance to an app.

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Eliciting Informed Priors for Small Population RCTs

Assessing current use of Bayesian methods in rare disease and small population randomised controlled trials (RCTs).

Team: Giles Partington, Suzie Cro, Alexina Mason, Victoria Cornelius

Large populations are often infeasible in the case of rare disease trials, making reaching sensible power calculations difficult. Alternatives such as observational studies are used instead, one such option is using a Bayesian approach. Bayesian methods require prior distributions for all unknown parameters. There are several ways of eliciting prior distributions. We were interested in identifying how often Bayesian methods are used, which elicitation methods they use, and how frequentist rare disease RCTs handle the lack of population.

The findings from this review will be added once published.