Neutrophil to lymphocyte ratio as a prognostic marker for cardiovascular outcomes in patients with ST-segment elevation myocardial infarction after percutaneous coronary intervention: A systematic review and meta-analysis

Neutrophil to lymphocyte ratio (NLR) has been considered a prognostic biomarker of mortality and other major cardiac events. This study investigates NLR's efficacy in predicting in-hospital and long-term outcomes in patients with ST-segment elevated myocardial infarction (STEMI) undergoing percutaneous coronary intervention (PCI). Electronic databases (PUBMED, Cochrane CENTRAL, ERIC, Embase, Ovid, and Google Scholar) were searched till June 2022 to identify studies having STEMI patients who underwent PCI. Risk ratios and mean differences (MDs), along with their corresponding 95% confidence intervals (Cis) and standard deviations (SDs), were pooled using a random-effect model. This meta-analysis has been registered on Prospero (ID: CRD42022344072). A total of 35 studies with 28,756 patients were included. Pooled estimates revealed an increased incidence of primary outcomes; in-hospital all-cause mortality (RR = 3.52; 95% CI = 2.93-4.24), long-term all-cause mortality (HR = 1.07; 95% CI = 1.00-1.14), (RR = 3.32; 95% CI = 2.57-4.30); in-hospital cardiovascular mortality (RR = 2.66; 95% CI = 2.04-3.48), long-term cardiovascular mortality (RR = 6.67; 95% CI = 4.06-10.95); in-hospital major adverse cardiovascular events (MACE) (RR = 1.31; 95% CI = 1.17-1.46), long-term MACE (RR = 2.92; 95% CI = 2.16-3.94); length of hospital stay (WMD = 0.60 days; 95% CI = 0.40-0.79) in patients with high NLR compared to those with a low NLR. NLR might be a valuable tool for prognostication (in-hospital) and stratification of patients with STEMI who underwent PCI.