Diagnostic and prognostic performance of the neutrophil- -to-lymphocyte ratio in acute coronary syndromes: A meta-analysis of 90 studies including 45 990 patients

Background: Cardiovascular disease is a leading cause of mortality worldwide and is likely to rise. Acute coronary syndrome (ACS) is consequent on inflammation. As a common and cost-effective inflammatory biomarker, the neutrophil-to-lymphocyte ratio (NLR) may be beneficial in cardiovascular medicine. Aims: This meta-analysis examines the diagnostic and prognostic performance of the NLR in ACS. Methods: We systematically searched PubMed Central, Medline, Scopus, EMBASE, Cochrane Central Register of Controlled Trials, and Clinicaltrial.gov databases. The search spanned from databases inception to January 10, 2024. The findings were aggregated into normalized mean differences with 95% confidence intervals. Results: Ninety articles, with 45 990 participants, were included. Pooled analysis of the NLR varied and was higher in ST-segment elevation myocardial infarction (STEMI) vs. non-ST-segment elevation myocardial infarction patients (4.94 ± 3.24 vs. 3.24 ± 2.74), acute myocardial infarction vs. unstable angina (4.47 ± 3.43 vs. 2.97 ± 1.58), ACS vs. stable angina (SA) (5.45 ± 4.28 vs. 2.46 ± 2.15), and ACS vs. controls (5.31 ± 4.01 vs. 2.46 ± 2.45). The NLR also was associated with ACS mortality, with survivors having lower results (3.67 ± 2.72 vs. 5.56 ± 3.93). Subanalysis showed that differences in the NLR were observed in STEMI survivors (4.28 ± 3.24 vs. 6.79 ± 3.98). Of ACS patients with major cardiovascular events (MACE) vs. without MACE, the NLR was 6.29 ± 4.89 vs. 3.82 ± 4.12. In STEMI patients, the NLR differed between those with and without MACE (6.99 ± 5.27 vs. 4.99 ± 4.12). Conclusions: The NLR is an effective tool for differentiating between different types of ACS. A high NLR is associated with ACS and increased MACE at 30 days. The NLR also appears to be a good predictor of MACE risk, at least in STEMI patients.