The prognostic values of neutrophil to lymphocyte ratio for outcomes in chronic obstructive pulmonary disease

OBJECTIVE: Neutrophil to lymphocyte ratio (NLR) is considered as an inflammatory biomarker for clinical outcomes in patients with chronic obstructive pulmonary disease (COPD). We aimed to conduct a meta-analysis to evaluate the prognostic values of NLR for the exacerbation and mortality in patients with COPD. METHODS: We searched the database of Cochrane Central Register of Controlled Trials, EMBASE, and PubMed, before September 2017. The eligible studies were retrieved by 2 authors independently following the criteria. The pooled odds ratios (ORs) of included studies were used to evaluate the prognostic values of NLR. Subgroup analyses were conducted to make the results more accurate. RESULTS: Nine studies with 5140 patients were enrolled in this analysis. The high NLR was associated with higher risk of exacerbation (OR: 3.81, 95% confidence interval [CI]: 1.20–12.13, P = .02) and mortality (OR: 2.60, 95% CI: 1.48–4.57, P < .01). By subgroup analysis, high NLR could predict the mortality in patients >70 years (OR: 2.16, 95% CI: 1.17–3.98, P = .01) but not in patients <70 years (OR: 4.08, 95% CI: 0.91–18.24, P = .07), and had a higher predictive ability in Asian group (OR: 3.64, 95% CI: 1.87–7.08, P < .01) than Eurasia group (OR: 1.82, 95% CI: 1.43–2.32, P < .01). In addition, high NLR could predict the short-term mortality (OR: 2.70, 95% CI: 1.10–6.63, P = .03) and the long-term mortality (OR: 2.61, 95% CI: 1.20–5.65, P = .02). CONCLUSIONS: The NLR may be an independent predictor for incidence of exacerbation in patients with COPD. In addition, high NLR may be associated with higher mortality in patients with COPD, especially for Asian and the patients with higher mean NLR.