Data extraction
All data including demographics (sex, age, weight), diagnosis (mild or severe cases), comorbidities (hypertension, diabetes, cardiovascular disease, respiratory system disease, past surgical history), laboratory assessments (lymphocyte, white blood cell, procalcitonin, C-reactive protein, erythrocyte sedimentation rate, D-Dimer), liver function (alanine aminotransferase ALT, aspartate aminotransferase AST), renal function (blood urea nitrogen BUN, creatinine), and length of hospital stay were extracted from electronic medical records (blood tests drawn on admission were obtained).