{ "background": "Evaluating health system interventions in low-resource settings requires robust, context-appropriate methodologies. Quasi-experimental designs are increasingly employed but their application for longitudinal clinical outcome assessment in district hospital systems remains methodologically underexplored.", "purpose and objectives": "This study aimed to methodologically assess the application of a quasi-experimental, difference-in-differences design for measuring longitudinal clinical outcomes within a national district hospital strengthening programme.", "methodology": "A longitudinal, controlled study was conducted across multiple district hospitals. Clinical outcome data were collected from routine health management information systems. The core analysis employed a difference-in-differences model: $Y{it} = \\beta0 + \\beta1 \\text{Treat}i + \\beta2 \\text{Post}t + \\beta3 (\\text{Treat}i \\times \\text{Post}t) + \\epsilon{it}$, where $Y_{it}$ is the clinical outcome for hospital $i$ at time $t$. Inference was based on cluster-robust standard errors.", "findings": "The methodological assessment demonstrated that the quasi-experimental design successfully isolated the programme effect from underlying temporal trends. A key empirical finding from the applied model indicated a statistically significant reduction in facility-based maternal mortality of 18.2% (95% CI: 12.5% to 23.7%) associated with the intervention hospitals relative to controls.", "conclusion": "The difference-in-differences approach provides a viable and rigorous methodological framework for evaluating clinical outcomes in longitudinal health systems research within operational district hospital settings.", "recommendations": "Future health systems evaluations in similar contexts should incorporate quasi-experimental designs with careful attention to parallel trends assumptions and the use of cluster-robust variance estimation. Routine data systems require continued strengthening to support such analyses.", "key words": "health systems research, quasi-experimental design, difference-in-differences, clinical outcomes, district hospitals, evaluation methodology",