Medical Sociology of Nurse-Led Hypertension Task Shifting and Diagnostic Retention in South African Primary Clinics: A Target-Trial Emulation of Scope-of-Practice Expansion

Task shifting of hypertension diagnosis and management to nurses in South African primary clinics has been promoted as a response to physician scarcity, yet the sociological conditions under which expanded nursing scope improves diagnostic retention remain poorly specified. Using a declared variance structure with between-cluster standard deviation of 6.0, residual standard deviation of 4.5, and intraclass correlation of 0.64, the analysis characterises power across cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points, with 2000 replications per design cell. The results indicate that 52 clusters are required to detect a 5 percentage point effect at 80% power, a requirement that exceeds the clinic counts typically available in district-level rollouts. Diagnostic retention is a sociological outcome shaped by professional boundary work, organisational trust and patient deference, and that BACI designs must be sized against the clustering induced by these social processes rather than against individual-level variation alone. The contribution is a methodological and conceptual specification of how scope-of-practice interventions should be evaluated when the outcome is a socially embedded clinical behaviour.