{ "background": "Strengthening primary healthcare is a critical policy goal in many African nations, yet robust evidence on the effectiveness of integrated urban primary care networks (PCNs) remains scarce. This gap hinders the efficient allocation of resources and scaling of successful models.", "purpose and objectives": "This study aimed to quantify the causal effect of a large-scale urban PCN intervention on key clinical outcomes in Kenya, specifically testing whether network integration improved management of hypertension and diabetes.", "methodology": "We employed a quasi-experimental difference-in-differences design. Longitudinal patient-level data were analysed from intervention clinics and matched control facilities. The core model is $Y{it} = \\beta0 + \\beta1 (\\text{Treat}i \\times \\text{Post}t) + \\gammai + \\deltat + \\epsilon{it}$, where $Y_{it}$ is the clinical outcome for clinic $i$ at time $t$. Inference was based on cluster-robust standard errors.", "findings": "The intervention was associated with a statistically significant 12.4 percentage-point increase (95% CI: 8.1, 16.7) in the proportion of hypertensive patients achieving controlled blood pressure. No significant effect was observed for glycaemic control in diabetic patients.", "conclusion": "Urban PCNs can significantly improve hypertension control, demonstrating their potential to enhance care for specific chronic conditions. The differential impact across diseases suggests that the intervention's mechanisms are condition-specific.", "recommendations": "Policy should prioritise the rollout of PCNs for hypertension management while designing complementary, targeted components for diabetes care. Future programmes should embed robust monitoring and evaluation frameworks from inception.", "key words": "primary health care, health systems, quasi-experimental, chronic disease, health policy, sub-Saharan Africa", "contribution statement": "This study provides the first application of a difference-in-differences framework to evaluate a nationwide PCN intervention in the region, generating novel causal evidence