Association of Neutrophil-to-Lymphocyte-Ratio and clinical outcomes in COPD

<bold>Background:</bold> Prognostic tools for management of COPD are warranted due to the complexity and the burden of the disease. The Neutrophil-to-Lymphocyte Ratio (NLR) is an emerging prognostic biomarker in various chronic and inflammatory diseases, this study aims to further investigate its role in COPD. <bold>Methods:</bold> This study is a secondary analysis of the COMIC Cohort. Patients with a complete blood count profile during hospitalisation for an acute COPD exacerbation (AECOPD) were included. Cox regression analyses determined the associations between NLR and all-cause mortality, severe AECOPD requiring hospitalisation, and development of community acquired pneumonia (CAP), all within a follow-up period of three years. Analyses were done for NLR as continuous variable and distributed into groups based on the median NLR and reference values (NLR ≤ 3, NLR 3-11, NLR ≥ 11). <bold>Results:</bold> 307 patients were included. The median NLR value was 6.22 (IQR 3.5-10.6). After adjustment, higher NLR was significantly associated with increased all-cause mortality, with a Hazard Ratio of 1.38 per 10 units NLR increase (95% CI: 1.09-1.75, p=.008). In multivariate analyses, no significant associations were found between all-cause mortality and NLR groups based on the used cut-off points. No significant relationships were observed between NLR and severe AECOPD or CAP during follow-up. <bold>Conclusion:</bold> When considered as continuous variable, higher NLR measured at hospitalisation for AECOPD is independently associated with increased risk of all-cause mortality. The utility of implementing a cut-off point is questionable, future studies should aim to elucidate more reliable and standardised NLR cut-off values.