Pilot and feasibility studies: is there a difference from each other and from a randomised controlled trial?

Area of Science:

• Clinical Trials Methodology
• Research Design
• Health Services Research

Background:

• Preliminary studies are vital before definitive trials but definitions of feasibility and pilot studies are often unclear and misused.
• Lack of clear definitions leads to inconsistent application and understanding of these critical research stages.

Purpose of the Study:

• To introduce the concepts of pilot and feasibility trials.
• To synthesize existing literature and funder guidance on defining pilot and feasibility studies.

Main Methods:

• A comprehensive review of published literature definitions and advice.
• Analysis of definitions and guidance from funder websites.
• Inclusion of examples illustrating good and poor practices in study design and reporting.

Main Results:

• Inconsistent terminology is used, with varying views on whether 'feasibility' and 'pilot' are synonymous or distinct.
• Consensus exists that feasibility/pilot studies should not test treatment comparisons or estimate effect sizes, though this is not always followed.
• Differentiation is proposed: 'feasibility' as an overarching term, 'pilot' for studies mimicking trial structures (e.g., control groups, randomization) but with distinct aims.

Conclusions:

• Recommend using 'feasibility' as the umbrella term for preliminary research.
• 'Pilot' studies should resemble the main trial but possess different objectives and plans for future work.
• Discourage labeling studies as 'pilot' if their primary aim is to evaluate treatment effects.