Pilot or feasibility trial
Can a later definitive trial be conducted, and what needs to change?
When to use this project
Resolve uncertainties about recruitment, delivery, retention, measurement or trial procedures before a larger evaluation. Prespecify criteria for proceeding, amending or stopping.
How it differs
Feasibility is the primary objective. A small efficacy trial is not automatically a pilot, and an imprecise treatment effect does not determine whether a definitive trial should proceed.
Decisions before you start
- State which later-trial uncertainties the pilot addresses and whether assignment is randomized.
- Choose progression criteria with justified denominators and contextual review, not only a significance test.
- Base sample size on feasibility information and precision. The randomized pilot CONSORT extension applies when the pilot is randomized.
How the flows work together
Each flow below links to its diagram, steps and tables. Flow order organizes the project; it does not imply that all work is strictly sequential. Data assessment, analysis planning and protocol refinement may inform one another.
1. Feasibility study overview
Overview · Question through future-study decisions
Use this overview to state the purpose and link to detailed decisions. Keep a versioned protocol and decision register, and add evidence references for the rationale.
2. Recruitment and intervention delivery
Conduct · Assess enrollment adherence and procedures
Measure the procedures the later trial depends on, including recruitment burden and intervention fidelity. Randomization may be piloted but is not mandatory for every feasibility study.
3. Feasibility endpoints and progression
Design · Define criteria for study progression
Feasibility endpoints answer whether and how to proceed. Prespecify progression criteria and their denominators; treatment efficacy is generally not the primary decision criterion in a feasibility pilot.
4. Sample size and precision
Statistics · Justify information needed for decisions
Choose information needs for the feasibility measures. Report interval uncertainty and operational assumptions; an arbitrary small sample or a definitive efficacy power calculation is not a substitute for this rationale.
5. Feasibility analysis and refinement
Statistics · Summarize findings and required changes
Combine numerical progression criteria with prespecified contextual review of delivery, acceptability and safety. Document amendments to the planned definitive trial rather than interpreting lack of statistical significance as lack of benefit.
Equations and statistical interpretation
These explanations describe notation and assumptions. Flow does not calculate these values.
Feasibility proportion
x is the number meeting a defined feasibility condition and n is the eligible denominator at the stated cutoff.
Recruitment and retention use different denominators. Report a suitable binomial interval, such as a Wilson interval, rather than treating the observed proportion as exact. Clustering requires adapted uncertainty estimation.
Published example
Read the phase II feasibility objectives and operational findings. Distinguish this report from the later definitive AVERT trial.
This publication illustrates a study design, not an endorsement of every method or a reproduction of its results. Follow its protocol, supplement and update history when studying the example.
Hypothetical scenario
A rehabilitation team wants to test whether patients can be recruited and retained for a future exercise trial.
- Feasibility study overview: Identify recruitment, adherence and follow-up uncertainties and register the interventional study prospectively.
- Recruitment and intervention delivery: Pilot consent, assignment if used, delivery and retention procedures.
- Feasibility endpoints and progression: Define recruitment and retention measures and explicit proceed, amend or stop criteria.
- Sample size and precision: Assess expected interval widths for the key feasibility proportions.
- Feasibility analysis and refinement: Apply the criteria with qualitative barriers and safety information, then document changes to the definitive trial.
Deliver a populated protocol, decision log, data specification, and planned outputs. Enter numerical findings only after analysis and verification. Keep decisions made before seeing results distinguishable from later amendments.
Sources
- CONSORT extension for randomized pilot and feasibility trials (2016)
- WHO: clinical trials and prospective registration
- WHO: primary registries in the trial registry network
- ISRCTN: what the clinical study registry records
- ClinicalTrials.gov: about the registry
Source check: 2026-09-17. Record the version of each reporting or appraisal tool used in your actual protocol.
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