CRP and chronic obstructive pulmonary disease: In the training set, the multivariate logistic regression analysis showed that age ≥ 60 years, comorbid chronic obstructive pulmonary disease (COPD), procalcitonin (PCT) ≥ 2 ng/mL, C-reactive protein (CRP) ≥ 100 mg/L, partial pressure of arterial oxygen (PaO2) < 60 mmHg, and partial pressure of arterial carbon dioxide (PaCO2) ≥ 50 mmHg were independent risk factors for poor efficacy (all p < 0.05).