Neutrophil to lymphocyte ratio for predicting delayed neurologic sequelae caused by carbon monoxide poisoning

BACKGROUND: This study summarized and analyzed the prognostic value of the neutrophil to lymphocyte ratio (NLR) for delayed neurologic sequelae (DNS) caused by carbon monoxide (CO) poisoning. METHODS: PubMed, Embase, Cochrane Library, Web of Science, ScienceDirect, and China National Knowledge Infrastructure Database were searched to identify relevant articles from their inception to February 2026. The odds ratio and its 95% confidence interval (CI), area under the curve, meta-regression analysis, sensitivity analysis, and publication bias for NLR were estimated to predict DNS. RESULTS: Eight studies were included, involving 1757 patients with acute CO poisoning, among whom 382 cases (21.7%) developed DNS. The pooled results show that NLR was related to DNS (odds ratio = 14.67, 95% CI: 8.26-26.04, P < .001) and had high heterogeneity (I2 = 65.1%, P = .005). The area under the curve of NLR for predicting DNS was 0.88 (95% CI: 0.85-0.91), with a sensitivity of 86% and a specificity of 72%. Subgroup analysis indicated that study design may be the source of heterogeneity. Sensitivity analysis suggested the robustness of the results. Deek's test did not detect significant publication bias (P = .24). CONCLUSION: Current evidence indicates that an elevated NLR is associated with an increased risk of DNS after acute CO poisoning, supporting its potential utility as a prognostic marker. However, because the included studies showed substantial heterogeneity and were predominantly retrospective, these findings should be interpreted with caution and require validation in high-quality prospective studies. NLR should therefore be considered an auxiliary tool for risk stratification rather than an independent diagnostic method. Its principal clinical value may lie in resource-limited settings where advanced monitoring is not feasible.