{ "background": "Community health centres are a cornerstone of primary care delivery in Nigeria, yet robust methodological approaches for evaluating their clinical performance over time are underdeveloped. The application of longitudinal analytical techniques, particularly panel-data estimation, remains inconsistent and poorly characterised in this context.", "purpose and objectives": "This systematic review aims to critically appraise the methodological application of panel-data models in assessing clinical outcomes within Nigerian community health centres, identifying common practices, strengths, and limitations.", "methodology": "A systematic search of multiple electronic databases was conducted for studies employing panel-data analysis. Included studies were screened and data extracted using a pre-defined protocol. Methodological quality was assessed via a bespoke tool focusing on model specification, handling of unobserved heterogeneity, and inference. The core model form evaluated was $y{it} = \\beta X{it} + \\alphai + \\epsilon{it}$, where $\\alpha_i$ denotes entity-specific effects.", "findings": "Of 42 included studies, a dominant theme was the frequent omission of tests for critical model assumptions, such as cross-sectional dependence. Only 24% adequately reported robust standard errors to account for potential heteroskedasticity and autocorrelation. The direction of association between resource availability and outpatient outcomes was consistently positive but statistically fragile in models neglecting time-invariant confounders.", "conclusion": "The methodological rigour of panel-data applications in this field is highly variable. Widespread oversight of fundamental econometric assumptions undermines the reliability of reported inferences and limits the utility of findings for policy.", "recommendations": "Future research must prioritise diagnostic testing and explicitly justify model selection between fixed- and random-effects estimators. Reporting should mandate details on handling of missing data, variance structure, and sensitivity analyses.", "key words": "panel data, health systems research, econometric evaluation, primary healthcare, longitudinal analysis, methodology", "contribution statement": "This review provides the first formal methodological audit of panel-data estimation practices in Nigerian health services research, establishing a