Neutrophil-lymphocyte ratio, monocyte-lymphocyte ratio, and platelet-lymphocyte ratio in stroke-associated pneumonia: a systematic review and meta-analysis

AbstractBackground Predicting stroke-associated pneumonia (SAP) is crucial for intensifying preventive measures and decreasing morbidity and mortality. This meta-analysis aims to evaluate the association between baseline neutrophil-lymphocyte ratio (NLR), monocyte-lymphocyte ratio (MLR), and platelet-lymphocyte ratio (PLR) with SAP and to determine the strength of the association.Methods The Web of Science, SCOPUS, and PUBMED databases were searched to find eligible studies. The standardized mean difference (SMD) and 95% confidence interval (CI) were used to evaluate the differences in NLR, MLR, and PLR levels between SAP and non-SAP patients. The meta-analysis was conducted using the software "Review Manager" (RevMan, version 5.4.1, September 2020). The random-effect model was used for the pooling analysis if there was substantial heterogeneity. Otherwise, the fixed-effect model was adopted.Results Twelve studies comprising 6302 stroke patients were included. The pooled analyses revealed that patients with SAP had significantly higher levels of NLR, MLR, and PLR than the non-SAP group. The SMD, 95% CI, p-value, and I2 for them were respectively reported as (0.88, 0.70–1.07, .00001, 77%); (0.94, 0.43–1.46, .0003, 93%); and (0.61, 0.47–0.75, .001, 0%). Subgroup analysis of NLR studies showed no significant differences in the effect size index between the severity of the stroke, the sample size, and the period between the stroke onset and the blood sampling.Conclusion This systematic review and meta-analysis suggest that an elevated NLR, MLR, and PLR were associated with SAP, indicating that they could be promising blood-based biomarkers for predicting SAP. Large-scale prospective studies from various ethnicities are recommended to validate this association before they can be applied in clinical practice.Keywords: Stroke-associated pneumonialymphocytemonocyteneutrophileplateletratio TransparencyDeclaration of financial/other relationshipsThe authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.AcknowledgementsAuthors would like to thank Institute of Postgraduate Studies (IPS), University Sains Malaysia (USM) for fellowship support [Ref. no. P-FD0006/20 (R)].Additional informationFundingThis paper was not funded.