CRP and Pleural effusion: After the LASSO regression selection, 25 candidate predictors were determined, including Age, Respiratory Rate, Calcium ions, Platelet, Neutrophil count, Lymphocyte, Globulin, Cholesterol, Pleural effusion, CT grade, Lactate, BMI, Temperature, Pulse, SBP, DBP, Red blood cell width, Blood Glucose, NLR, CRP, and NAR (Figures 2a,b).