Community Mental Health Service Task-Shifting Ratios and Psychosis Relapse Detection in Ethiopian District Clinics: A Stepped-Wedge Implementation Estimation

Task-shifting of community mental health services to non-specialist health workers in Ethiopian district clinics is promoted as a response to severe specialist shortages, yet the design parameters that determine whether such programmes can detect differences in psychosis relapse remain unexamined. the present analysis characterises the operating characteristics of a before-after-control-impact design for evaluating task-shifting ratios, using a replication-based power analysis under a declared variance structure with between-cluster standard deviation of 6.0, residual standard deviation of 4.5 and intraclass correlation of 0.64. Across 2000 replications per design cell and cluster counts of 8, 16, 24 and 32, the analysis estimated power at effect sizes of 3, 5 and 8 percentage points. Power reached 80% at 54 clusters for a 5-percentage-point effect, and the minimum detectable effect declined as cluster count increased. The intraclass correlation of 0.64 dominated the variance budget, meaning that additional clusters rather than additional patients within clusters carried most of the information. The results imply that district-level evaluations of task-shifting ratios require cluster counts well above those typical of pilot implementation studies, and that the before-after-control-impact estimator is defensible only when the cluster count is planned against the intraclass correlation rather than against the nominal sample size.