CRP and infection: Based on the above methods and analysis, the following categorical variables were analyzed by backward stepwise logistic regression: age, cerebrovascular disease, immunosuppression, fever, chest tightness, respiratory tract secondary infection, myocardial injury, AKI, sivelestat treatment, ICU admission, invasive mechanical ventilation, Omicron pneumonia, PO2/FiO2, Lac, white blood cell count, neutrophil count, lymphocyte count, CRP, PCT, IL-6, and d-dimer.