Model 8 included variables such as immunodeficiency, metastatic tumor, hepatic failure, residing at home independently, FiO2, chronic dialysis, ventilation mode, albumin, age, highest glucose, highest bilirubin, minute ventilation volume (i.e., the product of tidal volume multiplied by respiratory rate) and admission source (i.e., the location where the patient was immediately prior to ICU admission), showed the highest fitness value and was selected as the representative model. The gene discussed is ALB; the disease is immunodeficiency disease.