Fig. 4

ROC curve for risk factors of combined CD4⁺CD8⁺ T cells%, CAT score, and home oxygen therapy for predicting respiratory failure in patients with acute exacerbation of COPD. The sensitivity and specificity were 60.4% and 86.8%, respectively. COPD, chronic obstructive pulmonary disease; AUC, the area under the curve; Sen, sensitivity; Spe, specificity; Cov, cut-off value; ROC, receiver operating characteristic; CAT, chronic obstructive pulmonary disease assessment test