Pilot studies in clinical research

Pilot studies are small‐scale studies conducted to gather information and provide a foundation for the design of a definitive trial. They do not seek to estimate treatment efficacy or effectiveness themselves but may be used to assess whether a definitive trial is feasible and how it can be carried out.

The objectives of a study can be met only if a sufficient number of participants are recruited. A formal power calculation is not usually necessary for a pilot study where the focus is on estimation – for example, of feasibility parameters or the population variance – and the precision of these estimates. However, the sample size should still be justified as appropriate to meet the aims of the trial.

The appropriate analysis of a pilot study would usually be a descriptive summary of the parameters of interest, addressing the original trial objectives. The analysis should not contain hypothesis testing for which the trial is not powered. The interpretation of the results should be in line with the feasibility of the planned main trial. The decision‐making process and changes made to the trial design based on the pilot study should be documented, and results presented in accordance with the CONSORT extension for pilot trials. Every effort should be made to publish the trial for transparency and to allow learning to be shared within the research community.