The predictive value of C-reactive protein / albumin ratio and sarcopenia index for frequent acute exacerbation events in patients with chronic obstructive pulmonary disease

Background: To evaluate the prognostic significance of the C-reactive protein/albumin ratio (CAR) and sarcopenic index (SI) in predicting frequent acute exacerbations among patients with chronic obstructive pulmonary disease (COPD). Methods: A retrospective cohort study was conducted involving 205 patients hospitalized for acute exacerbations of COPD (AECOPD) between January 2020 and December 2022. Participants were stratified into non-frequent (n = 79) and frequent acute exacerbation groups (n = 126) based on the frequency of exacerbations during a 1-year follow-up. Laboratory parameters, including complete blood count, C-reactive protein (CRP), albumin, creatinine, cystatin C (Cys-C), and blood gas indices, measured within 24 hours of admission, were compared between groups. Least absolute shrinkage and selection operator (LASSO) regression and multivariate logistic analysis were employed to identify independent risk factors. The predictive performance of CAR and SI, both individually and in combination, was assessed using receiver operating characteristic (ROC) curve analysis. Results: The frequent exacerbation group exhibited significantly elevated levels of white blood cell (WBC) count, neutrophil percentage (Neut%), neutrophil count, neutrophil-to-lymphocyte ratio (NLR), CRP, CAR, Cys-C, lactate dehydrogenase (LDH), and partial pressure of carbon dioxide (PCO ₂ ), alongside reduced lymphocyte counts, prognostic nutritional index (PNI), albumin, creatinine, SI, and partial pressure of oxygen (PO ₂ ) compared to the non-frequent group (all P < 0.05). A higher prevalence of respiratory failure was also observed in the frequent exacerbation group (P < 0.05). Multivariate analysis identified WBC, PNI, CAR, SI, and PCO ₂ as independent predictors of frequent exacerbations (OR = 1.133, 1.090, 1.066; all P < 0.05). The combined model of CAR and SI, integrated with the base model (WBC + PNI + PCO ₂ ), demonstrated an area under the ROC curve (AUC) of 0.818 (95%CI: 0.756 – 0.880), outperforming models using CAR alone (AUC = 0.797) or SI alone (AUC = 0.795) in terms of sensitivity (0.738) and specificity (0.823). Conclusion: The synergistic application of CAR and SI is strongly associated with frequent acute exacerbations in COPD patients. This combination demonstrates superior predictive capacity compared to individual markers, offering a clinically valuable tool for identifying high-risk individuals.