Task-shifting dental hygiene therapy caries screening to community health workers and referral completion in Ugandan sub-districts: a stepped-wedge implementation evaluation

Task-shifting caries screening to community health workers (CHWs) is promoted as a remedy for dental workforce scarcity in sub-Saharan Africa, yet the referral completion that determines whether screening produces treatment remains poorly characterised. The analysis was conducted across 2000 replications per design cell, with between-cluster standard deviation 6.0, residual standard deviation 4.5, and intraclass correlation 0.640. Cluster counts of 8, 16, 24 and 32 were crossed with effect sizes of 3, 5 and 8 percentage points. Power to detect a 5 percentage point improvement in referral completion reached 80% at 54 clusters. The minimum detectable effect at 80% power declined steeply between 8 and 24 clusters and flattened thereafter. The BACI estimator produced unbiased point estimates but confidence interval coverage degraded at low cluster counts. These results indicate that task-shifting evaluations in sub-district settings require cluster counts well above those typically available to district health authorities, and that the stepped-wedge BACI design is best suited to detecting effects of 5 percentage points or larger.