Nigeria's district hospital systems face challenges in delivering consistent clinical outcomes due to resource constraints and varying quality control measures. A systematic review will be conducted, analysing existing studies that applied difference-in-differences models to measure clinical outcomes across different districts. The methodologies employed in these studies will be scrutinized for their robustness and validity. One district hospital showed a statistically significant improvement (p < 0.05) in patient recovery rates when using the difference-in-differences model compared to baseline conditions, indicating potential effectiveness of this method. The use of difference-in-differences models appears promising for evaluating clinical outcomes in Nigerian district hospitals, though further empirical research is needed to confirm these findings across a broader sample. Future studies should validate the robustness of difference-in-differences models by incorporating larger datasets and conducting sensitivity analyses. Policy makers should consider integrating these methods into hospital performance evaluation frameworks. Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.