Task-Shifted Trauma Care Fidelity Decay Under Supervision Sparsity in Rural Malawi: A Stepped-Wedge Implementation Trial Estimating Mental Health Symptom Trajectories

Task-shifted trauma care in rural Malawi depends on community health workers whose counselling fidelity may decay as supervision intervals lengthen, yet the supervision thresholds at which fidelity loss becomes clinically consequential remain unquantified. No observational data are reported: the analysis evaluates the design under a declared variance structure with between-cluster SD = 6.0, residual SD = 4.5 and intraclass correlation = 0.64, across 2000 replications per design cell. Power was estimated for cluster counts of 8, 16, 24 and 32 and effects of 3, 5 and 8 percentage points. Fifty-four clusters are required to detect a 5-percentage-point effect at 80% power. The results indicate that the design is adequately powered only at the upper end of the cluster range, that the minimum detectable effect falls steeply as clusters increase, and that the intraclass correlation of 0.64 dominates the precision of the fidelity-decay contrast. The contribution is a design-level demonstration that supervision-sparsity trials in task-shifted trauma care must be sized against clustering, not against individual-level symptom variance, and that fidelity decay should be modelled as a cluster-level process.