Relationship of Red Cell Index with the Severity of Chronic Obstructive Pulmonary Disease

Background: We aimed to investigate the association between red cell index (RCI) and the severity of Chronic Obstructive Pulmonary Disease (COPD), and compare predictive value of RCI, neutrophil-lymphocyte ratio (NLR) and platelet-lymphocyte ratio (PLR) for the severity of COPD.

Methods: A total of 207 participants were recruited (100 COPD patients and 107 healthy controls). COPD patients were divided into two groups according to the optimal cut-off value of RCI determined by the receiver operating characteristic (ROC) curve. Pearson's correlation test, logistic regression analysis and other tests were performed.

Results: Compared with low RCI group, the forced expiration volume in 1 second (FEV) and FEV in percent of the predicted value (FEV%) in high RCI group were lower ( = 0.016, = 0.001). There was a negative correlation between RCI and FEV% ( = -0.302, = 0.004), while no correlation between FEV% and NLR as well as PLR were found. RCI showed higher predictive value than NLR and PLR for predicting Global Initiative for Chronic Obstructive Lung Disease classification (GOLD), with a cut-off value of 1.75 and area under the curve (AUC) of 0.729 ( = 0.001). Multivariate logistic regression analysis proved that RCI was an independent factor for lung function in COPD patients (odds ratio [OR] = 4.27, 95% CI: 1.57-11.63, = 0.004).

Conclusion: RCI is a novel biomarker that can better assess pulmonary function and severity of COPD than NLR and PLR. Higher RCI is related to deterioration of pulmonary function.