{ "background": "Urban primary care networks are a cornerstone of health system reform in South Africa, yet robust methods for evaluating their clinical performance across heterogeneous sites are lacking. Existing evaluations often fail to account for multi-level data structures and produce unreliable estimates for smaller clinics.", "purpose and objectives": "This study aimed to develop and apply a novel Bayesian hierarchical model to measure and compare clinical outcomes across an urban primary care network, using hypertension control as a primary indicator. The objective was to provide a more statistically robust framework for health system evaluation.", "methodology": "We conducted an intervention study analysing routine clinical data from multiple primary healthcare facilities. The core model was specified as $y{ij} \\sim \\text{Bernoulli}(\\theta{ij}), \\; \\text{logit}(\\theta{ij}) = \\alpha + \\beta X{ij} + u{j}$, where $y{ij}$ is the control status for patient $i$ in facility $j$, $X{ij}$ are patient-level covariates, and $u{j} \\sim N(0, \\sigma^2_u)$ are facility-level random effects. Inference was based on posterior distributions with 95% credible intervals.", "findings": "The model revealed substantial variation in adjusted hypertension control rates between facilities, with a posterior probability of 0.87 that the true inter-facility standard deviation exceeded 0.2 on the log-odds scale. One network demonstrated a significantly higher pooled control rate (posterior median: 58%, 95% CrI: 52% to 64%) compared to others.", "conclusion": "The Bayesian hierarchical model successfully quantified clinical performance variation while stabilising estimates for smaller facilities, offering a superior methodological approach for network evaluation.", "recommendations": "Health authorities should adopt hierarchical modelling techniques for routine health system performance assessment. Future research should integrate this model with cost-effectiveness analyses.", "key words": "Bayesian hierarchical model, primary care networks, health systems evaluation, clinical