The independent variables included in the model were: influenza, immunosuppression, pregnancy, hematological disease, chronic renal failure, chronic heart disease, COPD, presence of shock on ICU admission, lactate, PCT, C-reactive protein (C-RP), creatinine, lactate dehydrogenase (LDH), creatine phosphokinase (CPK), SOFA score, APACHE II score, and age. Here, PIK3C2A is linked to chronic obstructive pulmonary disease.