Criteria for proceeding to a definitive trial | Assessment | Criterion fulfilled? | Evidence |
---|---|---|---|
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. | Yes | Response to postal invitation was high at 68% overall and 27% of responders interested and self-reporting as eligible for the study. |
An acceptable proportion of individuals responding to recruitment invitations are eligible to participate. | Screening records show a screen-failure rate of < 80%. | Yes | The screen-failure rate at clinical screening was 74%. |
Attrition from the exploratory 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. | Yes | Excluding deaths and formal withdrawals, only one participant was lost to follow-up at 6 months (2%). |
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. | Yes | Adherence was very high; 91% of intervention participants received at least one face-to-face and five telephone sessions. |
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. | Yes | Practices and participants from a variety of sociodemographic backgrounds were involved in the study. |
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. | Yes | Collection of data on PAF contact time is feasible and could be employed alongside standard trial methods for monitoring costs. |
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. | Yes—with modification (PASE questionnaire) | Measurement of outcomes was acceptable and largely feasible. However, the pilot study revealed issues with some self-report instruments and ascertainment of these outcomes would need to be modified in any potential future 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. | Yes | Sample size calculations under a range of parameters all suggest a definitive trial is achievable. |