Crossover trial overview — Randomized crossover trial

Question

Define the interventions and within-participant comparison of interest.

Assess crossover suitability

Assess disease stability, reversibility, carryover and whether period lengths and washout are defensible.

Protocol and registration

Prespecify sequences, period effects, missingness and analysis; obtain approvals and register prospectively.

Recruit

Enroll the intended stable population and record eligibility, consent and baseline measurements.

Randomize sequences

Randomize and conceal treatment sequence assignment; specify blinding and allocation procedures.

Treat across periods

Deliver treatments in assigned periods and record washout, adherence, deviations and discontinuation.

Assess outcomes

Measure endpoints at comparable times within each period and document incomplete pairs or periods.

Analyze within participants

Use the planned repeated-measure model; address period and carryover assumptions without choosing analysis from a preliminary carryover test.

Report

Report sequence allocation, participant-period flow and treatment estimates with the crossover reporting extension.

Crossover trial overview

End flow

Protocol and decision register

Record the protocol, approvals and registration where applicable. Preserve planned decisions and amendments separately from results.

Protocol and rationale evidence

Attach the dated protocol, approvals and amendments. A clinical trial registry publicly records the trial plan, such as ClinicalTrials.gov or an eligible WHO primary registry such as ISRCTN. Record the registry name, identifier and registration date before first enrollment. WHO ICTRP is a search platform, not itself a registry. Registration does not imply randomization.