{ "background": "Community health centres are critical nodes in primary healthcare systems, yet robust methodological frameworks for evaluating their operational reliability are underdeveloped. This creates a significant evidence gap for health systems planning and resource allocation.", "purpose and objectives": "This case study aims to methodologically evaluate the reliability of service systems in a network of community health centres. Its primary objective is to demonstrate the application of a quasi-experimental difference-in-differences (DiD) model to isolate the effect of a systemic intervention on facility reliability.", "methodology": "We employ a longitudinal DiD design, analysing panel data from intervention and matched control facilities. The core statistical model is $Y{it} = \\beta0 + \\beta1 \\text{Treat}i + \\beta2 \\text{Post}t + \\delta (\\text{Treat}i \\times \\text{Post}t) + \\epsilon{it}$, where $Y{it}$ is a composite reliability index. Inference is based on cluster-robust standard errors to account for facility-level correlation.", "findings": "The DiD estimator ($\\delta$) indicated a positive and statistically significant improvement in system reliability for intervention centres. The point estimate corresponded to a 17.5 percentage point increase in the composite reliability index (95% CI: 9.2, 25.8) relative to control facilities, with the effect being robust to several sensitivity checks.", "conclusion": "The applied DiD model provides a rigorous methodological framework for attributing changes in health system performance to specific interventions, moving beyond descriptive assessments. It demonstrates the value of quasi-experimental designs in operational health systems research.", "recommendations": "Health systems researchers should adopt quasi-experimental designs like DiD for evaluating complex service delivery interventions. Policymakers should mandate the collection of longitudinal, facility-level data to enable such analyses for evidence-informed decision-making.", "key words": "health systems research, difference-in-differences, quasi-experimental design,