Point-of-care salivary diagnostics in dental hygiene therapy and antibiotic prescribing for periodontal care in Nigerian clinics: a stepped-wedge estimation of diagnostic-stewardship thresholds

Point-of-care salivary diagnostics promise to reduce empirical antibiotic prescribing in periodontal care, but the design parameters that would allow a stepped-wedge trial to detect a stewardship effect in Nigerian dental clinics remain uncharacterised. The analysis characterises operating characteristics rather than reporting observational data. Power curves, minimum detectable effect curves, and coefficient plots were generated for cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points. The intraclass correlation of 0.64 dominates the design: at 8 clusters, power at a 5-percentage-point effect is low, and 54 clusters are required to reach 80% power at that effect. The minimum detectable effect at 80% power falls steeply as clusters increase from 8 to 32. The results imply that diagnostic-stewardship thresholds in Nigerian periodontal care cannot be estimated reliably with the small cluster counts typical of single-region trials, and that the before-after-control-impact design is defensible only when the cluster count approaches the 54-cluster benchmark.