Pilot and feasibility trials: what they test

Pilot and feasibility trials ask whether a future trial can be done, whether it should be done and, if so, how. A pilot runs the future trial, or part of it, on a smaller scale. Anyone who plans a definitive randomised controlled trial meets these questions first.

Their primary aim is to assess whether the future trial is feasible, not whether an intervention works. For that reason, an extension to the Consolidated Standards of Reporting Trials, or CONSORT, sets out how to report them.

The difference in purpose shapes everything from the number of participants to the reading of the results. Above all, it shapes the decision at the end: whether to proceed.

What pilot and feasibility trials are

The CONSORT statement is a guideline to improve the transparency and quality of the reporting of randomised controlled trials. In 2016 the BMJ published an extension of it for randomised pilot and feasibility trials, agreed by a consensus group.

The extension rests on a framework of its own. In that framework, a feasibility study for a future definitive trial asks whether the future trial can be done, should be done and, if so, how.

Pilot studies, in turn, are a subset of feasibility studies. They ask the same questions, but they have a particular design feature. In a pilot, the future definitive trial, or part of it, runs on a smaller scale, whether randomised or not.

The word definitive has a specific meaning here. It refers to a trial with appropriate power that focuses on effectiveness or efficacy.

How a pilot trial differs from the definitive trial

The two kinds of trial have different purposes. A pilot trial assesses feasibility, while the definitive trial assesses effectiveness or efficacy. As a result, the extension holds that the focus of the reporting should differ too.

Safety and potential effectiveness usually matter less in a pilot trial. Instead, the focus is on developing the intervention and its evaluation, where questions of feasibility might be different.

Several practical points follow in the extension.

• The number of participants should rest on the feasibility objectives, with some rationale given.
• The extension does not recommend formal hypothesis testing for effectiveness, or efficacy.
• The methods for each objective of the pilot trial can be qualitative or quantitative.

Deciding whether to proceed

A pilot trial exists to assess the feasibility of proceeding to the definitive trial. Accordingly, the extension asks that its design include a decision process about how to proceed.

That process might involve formal progression criteria. These decide whether to proceed, to proceed with amendments, or not to proceed at all.

The extension therefore adds two items to the report. The first is the prespecified criteria for judging whether, or how, to proceed with the definitive trial. The second is the implications for progression from the pilot to that trial, including any proposed amendments.

The extension also notes that, in the United Kingdom, the National Institute for Health Research requires pilot or feasibility studies to have clear criteria for deciding whether or not to progress to the next stage.

Richnovex's first phase, Discovery & Strategy, covers assessing the current idea, prototype or business state, defining goals, and implementing the roadmap, as its approach to that phase sets out. The phase ends with the goals set and the roadmap in hand.

Reporting pilot and feasibility trials

The extension applies to any randomised trial that runs a future definitive trial, or part of it, on a smaller scale. In its own words, the need for high standards in conduct and reporting applies just as much to pilot and feasibility trials as it does to definitive trials.

To that end, the published extension includes a checklist of 26 items, and a separate checklist for the abstract. It also includes a template for a CONSORT flowchart. Finally, it explains each change it made, with supporting examples.

A pilot ends in a decision to proceed

Pilot and feasibility trials assess whether a definitive trial is feasible, rather than whether an intervention works. For this reason, they end in a decision about how to proceed, which their design sets up from the start.

Sources

1. Eldridge SM and others, CONSORT 2010 statement: extension to randomised pilot and feasibility trials, BMJ (2016): doi.org/10.1136/bmj.i5239