With the proposed XGB method, the predictor factors or variables associated with a worse outcome in critically ill COVID-19 patients in terms of mortality were: age; high BMI; elevated ferritin, LDH, CRP, and creatinine levels; lymphopenia; low PaFi values; use of IMV; and abnormal values in hemostasis and coagulation, namely elevated PT and aPTT, elevated D-dimer and fibrinogen, and low platelet levels. Here, CRP is linked to lymphopenia.