Statistical analysis plan
depression/anxiety
REGRESSION, RECRUITMENT
A fully documented statistical analysis plan (SAP), centred on describing key process measures to decide if a definitive trial is feasible, will be prepared by the statistician (SAP), formally agreed with coinvestigators and the trial steering committee (TSC) prior to data collection being completed. Participant throughput will be summarised in an extended Consolidated Standards of Reporting Trials (CONSORT) diagram.Feasibility outcomes will be summarised using descriptive statistics, with 95% CIs provided to permit assumptions when planning a future definitive trial. Data relating to referral, screening and enrolment, and recruitment logs will be used to produce accurate estimates of eligibility, consent and recruitment rates.Treatment assignation, intervention adherence (eg, ACT session attendance) and satisfaction of care data will be used to contribute to the evaluation of the acceptability of randomisation and allocated intervention/treatment arms. At each time point, the time taken (per participant) to complete trial measures will be recorded. Retention rates will also be estimated for each of the patient-reported/clinical outcome measures, with consideration given to differential dropout between the arms of the trial to identify potential (attrition) bias in treatment completion and/or data collection. All feasibility outcomes will be compared with full-trial progression criteria.Baseline characteristics will be reported according to treatment arm. Continuous variables will be reported as mean (SD) if normally distributed or median (IQR) if non-normal, while categorical variables will be presented as frequency (%). Subsequent analyses will summarise the proposed patient-reported and clinical outcomes (eg, psychological flexibility, subjective memory function, quality of life and depression/anxiety measures) at each time point for each trial arm using appropriate descriptive statistics (eg, group mean, SD). To provide an indication of potential changes in scores/frequencies between the four time points, linear/logistic mixed effects regression models will be employed performed on an intention-to-treat (ITT) basis (accounting for data assumed to be missing at random). These random intercept (mixed) models will include intervention group, time, and intervention group by time interaction. There will be no emphasis on hypothesis testing, however, which is reserved for the future main trial. Rather, pre-to-post-intervention standardised effect sizes (Hedges’ g, relative risk) will be computed (SDs will be computed from estimated model SEs) with associated CIs calculated to explore imprecision around effect sizes.