Neutrophil to lymphocyte ratio in relation to risk of all-cause mortality and cardiovascular events among patients undergoing angiography or cardiac revascularization: A meta-analysis of observational studies

Objective The aim of this study was to investigate whether neutrophil to lymphocyte ratio (NLR) was an independent predictor for all-cause mortality or cardiovascular events in patients undergoing angiography or cardiac revascularization with observational studies by meta-analysis. Methods Pubmed and Embase were searched without language restrictions for cohort studies published prior to November 2013. Citations were independently screened by 2 authors, and those meeting the inclusion criteria defined a priori were retained. Data on authors, year of publication, location, target participant, comparison of NLR, outcome assessment, number of event and sample size, duration and statistical adjustments were abstracted. Results Eight studies were identified that reported on all-cause mortality and five studies were identified that reported on cardiovascular events. The pooled relative risk (RR) of all-cause mortality was 2.33 (95% CI 1.88–2.88) and the RR of cardiovascular events was 1.89 (95% CI 1.42, 2.52) comparing the highest with the lowest category of NLR. Conclusions The meta-analysis indicates that NLR is a predictor of all-cause mortality and cardiovascular events. Further well-designed trials are warranted to confirm this association.