Prognostic Nutritional Index as a Predictor of 30-Day Mortality Among Patients Admitted to Intensive Care Unit with Acute Exacerbation of Chronic Obstructive Pulmonary Disease: A Single-Center Retrospective Cohort Study

BACKGROUND: Acute exacerbation of chronic obstructive pulmonary disease (AECOPD) is significantly associated with increased mortality. The current study aimed to investigate the predictive ability of the prognostic nutritional index (PNI) in 30-day mortality among AECOPD patients admitted to the ICU. MATERIAL/METHODS: Clinical data were extracted from the Medical Information Mart for Intensive Care-III (MIMIC-III) database. Patients were divided into 3 groups according to the tertiles of PNI. Cox proportional hazard regressions were performed to assess the association between PNI and 30-day mortality. Subgroup analyses were performed to identify the consistency of the association. Receiver operator characteristic (ROC) curve analysis was performed to evaluate the predictive accuracy among PNI, serum albumin, neutrophil-to-lymphocyte (NLR), and platelet-to-lymphocyte ratio (PLR). RESULTS: A total of 494 AECOPD patients were included in this study. The mean age was 70.8±10.4 years old. Kaplan-Meier analysis showed ongoing divergence in rates of mortality among tertiles (p<0.001). After adjusting for confounders, high PNI tertile was an independent favorable predictor of 30-day mortality (HR=0.39; 95% CI, 0.19–0.80; p=0.011) compared to low tertile reference. Subgroup analysis showed that the predictive ability of PNI was especially suitable for patients aged >70 years and with mechanical ventilation. The cut-off value of PNI was 31.8 with sensitivity 62.3% and specificity 64.1%. The area under the ROC of PNI (0.642, 95% CI, 0.560 to 0.717) was better than that of serum albumin, NLR, and PLR. CONCLUSIONS: PNI could serve as a simple and reliable prognostic biomarker for AECOPD patients in the ICU.