Impact of neutrophils to lymphocytes ratio on major clinical outcomes in patients with acute coronary syndromes: A systematic review and meta-analysis of the literature

Background: Inflammatory markers are significantly associated with cardiovascular disease. The ratio between neutrophils and lymphocytes (NLR) is a potential new biomarker, which can single out individuals at risk for future cardiovascular events. Among total white blood cell count (WBC) and its subtypes, NLR seems to have the greatest predictive value for death and major adverse cardiovascular events (MACE) in patients with acute coronary syndrome (ACS). We conducted a meta-analysis of the literature to assess the relation between NLR and cardiovascular outcomes in STEMI/NSTEMI patients. Methods: MEDLINE and EMBASE databases were searched. Two reviewers selected studies and extracted data. Pooled results were reported as odds ratios (ORs) and were presented with the corresponding 95% confidence intervals (CI). Results: Twenty-three studies for a total of >16,000 patients were included. Compared to those with low NLR, high NLR on-admission was associated with a higher overall mortality both in patients with STEMI (OR: 4.60, 95% CI: 2.84–7.45; P < 0.00001) and in patients with NSTEMI (OR: 6.41, 95% CI: 2.65–15.50; P < 0.00001). An increased MACE risk was found in STEMI patients with high NLR (OR: 3.71, 95% CI: 2.67–5.17; P < 0.00001). Post-PCI mortality risk was significantly increased in patients with high NLR (OR: 3.76, 95% CI: 2.64–5.34; P < 0.00001). Conclusions: In this large meta-analysis on prognostic significance of NLR in ACS we found that on-admission high NLR in patients with STEMI/NSTEMI appeared to affect clinically important outcomes including both in-hospital and long-term mortality and MACE.