Table 1

Feasibility outcomes and success criteria for proceeding to a definitive randomised controlled trial

Feasibility outcomeDetails of feasibility outcomeSuccess criterion
Peer mentor recruitment rateNumber of peer mentors trained divided by the number individuals who were eligible for the peer mentor role1. Demonstration that the intervention can be delivered in practice and is acceptable to participants and peer mentors*
Peer mentor attrition rateNumber of peer mentors who were not matched with a participant divided by the number of peer mentors trained
Intervention completion rateNumber of participants who completed at least three peer mentorship sessions divided by the number of participants who commenced the intervention
Participant recruitment rateNumber of participants randomised divided by the number of individuals who were eligible to participate2. ≥60% of eligible individuals recruited
Attrition rate overall and in each groupNumber of participants who did not complete the 6-month questionnaire divided by the number of participants randomised3. <20% participant attrition with no evidence of attrition bias
Sample size required for a definitive RCTSample size calculation using the feasibility trial PIH scale scores assuming: 5% significance level; minimum power of 0.8; and 1:1 allocation ratio. The PIH scale scores were used because the PIH scale was chosen as the provisional primary outcome measure.4. Calculation of a sample size that is achievable in a main trial
Questionnaire completion rateNumber of questionnaires completed divided by the number of participants provided with the questionnairesNone specified for these feasibility outcomes
Intervention fidelityContent analysis of the mentors’ session summaries
Cost of delivering the mentor training eventEstimation based on the events delivered by the trial team members accounting for: staff salary, national insurance and pension contributions; resources; refreshments; and peer mentor travel expenses; but not venue hire, estates and indirect costs
Cost of delivering the interventionEstimation based on the volunteer coordinator and peer mentor costs, excluding the training costs
  • *No minimum/maximum rates were prespecified as acceptable for this success criterion.

  • PIH scale, revised 12-item Partners In Health scale; RCT, randomised controlled trial.