CRP and Pleural effusion: Twenty-six variables, including sex, age, peak body temperature, presence of hypoxemia, WBC, N%, L%, PLT, ESR, CRP, PCT, IL-6, La, AST, ALT, CK, CK-MB, LDH, FER, APTT, FG, D-dimer, IgE, atelectasis, pleural thickening and pleural effusion (Fig. 2-A), which might predict PB formation were included in the LASSO regression based on the development dataset.