Table 1 Pre-specified feasibility criteria
Criteria for proceeding to definitive trial | Assessment | Linked objective |
|---|---|---|
An acceptable proportion of individuals respond to recruitment invitations. | Recruitment records show an initial response rate of > 10% to postal invitation and/or > 25% to primary care practitioner invitation or waiting room recruitment. The three methods will be compared. | (1) Test the effectiveness of methods of recruitment and enrolment |
An acceptable proportion of individuals responding to recruitment invitations are eligible to participate. | Screening records show a screen-failure rate of < 80%. | (1) Test the effectiveness of methods of recruitment and enrolment |
Attrition from the pilot trial is low. | Trial records show that the proportion of enrolled participants “lost to follow-up” at 6 months is < 20%, excluding deaths and long-term care or hospitalisation. | (2) Assess retention and adherence to the study and/or intervention |
PAF intervention attracts high rates of participation from eligible adults. | Trial records indicate that adherence to the intervention is high; ≥ 65% of intervention participants participate in at least one face-to-face and five telephone sessions. | (2) Assess retention and adherence to the study and/or intervention |
PAF can engage individuals from a range of socio-economic localities. | Participants are recruited from primary care practices in wards with high deprivation scores and low deprivation scores. | (1) Test the effectiveness of methods of recruitment and enrolment |
PAF delivery costs can be recorded in a way that enables cost-effectiveness analysis. | Systems developed in the exploratory trial can be used to monitor the costs of a definitive RCT. | (3) Evaluate the methods of data collection and analysis for a definitive trial |
Methods for measuring primary and secondary outcomes and mediator variables are feasible and acceptable. | Process evaluation findings and completed questionnaires suggest that self-report and objective measures were comprehensible and acceptable to > 80% of participants. | (3) Evaluate the methods of data collection and analysis for a definitive trial |
The sample size required for an adequately powered trial is achievable. | Measurement variability of the primary outcome, recruitment rates, and expected attrition are consistent with a sample size that can be achieved within a reasonable time. | (4) Provide estimates of the variability of key outcomes to enable estimation of the sample size and resources required for a future definitive trial |