Trauma Ward Mental Health Family Bedside Presence Restrictions and Post-Traumatic Stress Disorder Symptom Onset Among Zambian Inpatients: A Target-Trial Emulation of Visitor Exclusion Thresholds

Visitor exclusion policies in trauma wards are common but their relationship to post-traumatic stress disorder (PTSD) symptom onset among inpatients remains poorly characterised. The analysis characterised the operating characteristics of the design across 2000 replications per cell, with between-cluster standard deviation of 6.0, residual standard deviation of 4.5, and an intraclass correlation of 0.640. Power was estimated for cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points. The design achieved 80% power to detect a 5-percentage-point effect with 56 clusters. Minimum detectable effects at 80% power declined as cluster count increased. The results indicate that the BACI estimator can identify clinically meaningful visitor exclusion thresholds in Zambian trauma wards, but only at cluster counts substantially larger than those typical of single-site studies. Visitor restriction research must treat cluster-level variance as a primary design parameter rather than a nuisance, and that threshold-based policies require evaluation designs capable of distinguishing ward-level policy effects from patient-level symptom trajectories.