Relationship between neutrophil lymphocyte ratio and red blood cell distribution width and respiratory failure in COPD patients

The neutrophil lymphocyte ratio (NLR) and red blood cell distribution width (RDW) have been repeatedly demonstrated to be associated with risk of severity, progression, and prognosis of chronic obstructive pulmonary disease (COPD), but data on respiratory failure (RF) in patients with COPD are very limited. This study aimed to examine the relationship between NLR and RDW and the incident RF in patients with COPD. This is a retrospective study that reviewed data by examining the hospitalization medical records to identify those who were admitted with a diagnosis of COPD. Based on whether RF occurred during index hospitalization, patients were classified as COPD group and COPD combined with RF group. Also, healthy controls of the same age and sex were enrolled in a 1:1 ratio as the COPD group. Univariate comparisons were performed between three groups to examine differences. With the COPD group as reference, multivariable logistic regression was formed to identify the relationship between NLR and RDW and RF, with adjustment for multiple covariates. There were 136 healthy controls, 136 COPD patients and 62 patients with COPD combined with RF included for analysis. There was a significant difference for eight variables, including age, WBC, neutrophil, NLR, RDW, platelet, PLR, and CRP. The Spearman test showed the significant correlation between NLR and WBC (correlation coefficient, 0.38; P = .008), NLR and RDW (correlation coefficient, 0.32; P = .013), and NLR and CRP level (correlation coefficient, 0.54; P < .001). The multivariable logistic regression showed that age (every additional 10 years) (OR, 1.785), NLR (OR, 1.716), RDW (OR, 2.266), and CRP (OR, 1.163) were independently associated with an increased risk of RF. This study demonstrated the independent associative effect of NLR and RDW with RF in patients with COPD, exhibiting the potential clinical role in evaluating the progress of COPD to RF.