{ "background": "Public health surveillance is a cornerstone of effective health systems, yet rigorous economic evaluations of such systems in low-resource settings are scarce. Rwanda has implemented several innovative surveillance programmes, but a synthesis of methodological approaches for assessing their cost-effectiveness is lacking.", "purpose and objectives": "This systematic review aims to identify, appraise, and synthesise methodological frameworks used in randomised field trials to evaluate the cost-effectiveness of public health surveillance systems in Rwanda.", "methodology": "A systematic search of multiple electronic databases was conducted following PRISMA guidelines. Studies were included if they were randomised field trials reporting a full economic evaluation of a surveillance system. Data were extracted on study design, outcome measures, cost categories, and analytical models. The primary model for synthesising incremental cost-effectiveness ratios (ICERs) was $\\text{ICER} = (C1 - C0) / (E1 - E0)$, where $C$ and $E$ denote costs and effects for intervention (1) and comparator (0). Study quality was assessed using the CHEERS checklist.", "findings": "Only three studies met the inclusion criteria. A key theme was the consistent use of a health systems perspective, but with substantial heterogeneity in cost inclusion. One trial reported a 95% confidence interval for the ICER that spanned all four quadrants of the cost-effectiveness plane, indicating high uncertainty. No study incorporated productivity losses or used a dynamic transmission model.", "conclusion": "The evidence base from randomised trials is extremely limited. Existing evaluations exhibit major methodological inconsistencies, particularly in cost measurement and handling of uncertainty, which impedes comparative analysis and policy generalisation.", "recommendations": "Future trials should adopt a standardised reference case for cost-effectiveness analysis tailored to surveillance systems, mandate the reporting of cost-effectiveness acceptability curves, and incorporate modelling of downstream transmission effects to capture full societal value.", "key words": "economic evaluation, health economics, incremental cost-effectiveness ratio, infectious disease, sub-Saharan Africa",