{ "background": "District hospitals in sub-Saharan Africa face severe resource constraints, yet rigorous, field-based evaluations of systemic efficiency interventions are scarce. Existing studies often rely on observational data, limiting causal inference about operational improvements.", "purpose and objectives": "This case study aims to methodologically evaluate the implementation of a randomised field trial designed to measure efficiency gains from a lean management intervention in district hospital systems. The primary objective is to assess the trial's design, execution, and analytical robustness.", "methodology": "We conducted a methodological evaluation of a cluster-randomised controlled trial across 24 district hospitals. The core efficiency outcome, patient throughput time, was modelled using a hierarchical linear model: $Y{ij} = \\beta0 + \\beta1 Tj + \\gamma X{ij} + uj + \\epsilon{ij}$, where $i$ indexes patients, $j$ hospitals, $Tj$ is the treatment assignment, and $u_j$ are cluster random effects. Inference was based on cluster-robust standard errors.", "findings": "The trial successfully demonstrated a significant reduction in median patient throughput time in intervention hospitals (15.2% decrease, 95% CI: 8.7% to 21.5%). Methodologically, key challenges included contamination control between clusters and the accurate daily capture of time-motion data. The intervention's effect was heterogeneous, with larger gains observed in hospitals with pre-existing electronic record systems.", "conclusion": "Randomised field trials are methodologically feasible for evaluating health systems efficiency interventions in resource-limited settings, but require meticulous design to address contextual complexities like inter-facility communication and data infrastructure variability.", "recommendations": "Future health systems trials should incorporate pre-trial process mapping to identify contamination risks and invest in simple, robust data capture tools tailored to local workflows. Analytical plans must pre-specify tests for heterogeneity of treatment effects.", "key words": "health systems research, operational efficiency, cluster randomised trial, lean management, implementation science