Defining the role of neutrophil-to-lymphocyte ratio in COPD: a systematic literature review

Abstract

COPD is characterized by a pulmonary and systemic inflammatory process. Several authors have reported the elevation of multiple inflammatory markers in patients with COPD; however, their use in routine clinical practice has limitations. The neutrophil-to-lymphocyte ratio (NLR) is a useful and cost-effective inflammatory marker derived from routine complete blood count. We performed a systematic literature review using the PRISMA statement. Twenty-two articles were included, recruiting 7,601 COPD patients and 784 healthy controls. Compared with controls, COPD patients had significantly higher NLR values. We found a significant correlation between the NLR and clinical/functional parameters (FEV₁, mMRC, and BODE index) in COPD patients. Elevation of the NLR is associated with the diagnosis of acute exacerbation of COPD (pooled data propose a cut-off value of 3.34 with a median sensitivity, specificity, and area under the curve of 80%, 86%, and 0.86, respectively). Additionally, increased NLR is also associated with the diagnosis of a bacterial infection in exacerbated patients, with a cut-off value of 7.30, although with a low sensitivity and specificity. The NLR is an independent predictor of in-hospital and late mortality after exacerbation. In conclusion, the NLR could be a useful marker in COPD patients; however, further studies are needed to better identify the clinical value of the NLR.

Keywords:

• acute exacerbations of COPD
• bacterial infection
• mortality in COPD
• inflammatory biomarkers
• eosinophilia
• GOLD stage

Acknowledgments

The publication of this systematic review was supported by a grant from the Instituto de Salud Carlos III (Grant FIS-PI16/00193, co-funded by European Regional Development Fund [ERDF], a way to build Europe) to Salud Santos. The authors received no compensation related to the development of the manuscript.

Author contributions

All authors contributed toward data acquisition, analysis and interpretation of results, drafting and critically revising the paper, gave final approval of the version to be published, and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.