Predictive Value of the Neutrophil-to-Lymphocyte Ratio/Serum Albumin for All-Cause Mortality in Critically Ill Patients Suffering from COPD.

Background: Among critically ill patients, chronic obstructive pulmonary disease (COPD) is an independent risk factor for death. Recently, biomarkers such as neutrophil-lymphocyte ratio (NLR) and albumin (ALB) have been used to predict the prognosis in patients with COPD. However, the association between NLR/ALB and all-cause mortality in critically ill COPD patients remains unclear. This study aims to explore the association between the NLR/ALB and prognosis in critically ill patients with COPD.

Methods: Data was sourced from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. Primary outcome was 28-day all-cause mortality, with secondary outcomes being in-hospital and 90-day all-cause mortality. The area under the receiver operating characteristic curve (AUROC) was calculated to compare prognostic accuracy of NLR, NLR/ALB, PLR, SII and MLR variables. After identifying the most predictive factor, KM survival curves, Cox models and subgroup analyses were used to examine NLR/ALB's relationship with mortality in critically ill COPD patients. Additionally, patients with COPD from the National Health and Nutrition Examination Survey data (1999-2018) was used with Cox regression to investigate NLR/ALB's correlation with all-cause mortality in COPD patients.

Results: 1916 critically ill COPD patients from MIMIC IV, divided into quartiles by NLR/ALB levels: Q1 (NLR/ALB<1.108), Q2 (2.095>NLR/ALB≥1.108), Q3 (4.221>NLR/ALB≥2.095), Q4 (NLR/ALB≥4.221). In multivariate Cox regression, Q4 vs Q1: 28-day mortality HR=2.27 (95% CI: 1.63-3.16); 90-day mortality HR=2.06 (95% CI: 1.56-2.71); in-hospital mortality HR=1.93 (95% CI: 1.35-2.77); P<0.001. Subgroup analyses showed that the correlation between NLR/ALB and 28-day mortality was stable Additionally, we recruited 2,003 COPD patients from the NHANES that found NLR/ALB also correlated with all-cause mortality in COPD (In multivariate Cox regression: Q4 vs Q1 hR=1.92 (95% CI: 1.45-2.55, P<0.001)).

Conclusion: Elevated NLR/ALB levels are associated with increased all-cause mortality in critically ill patients with COPD.