F2 and chronic kidney disease: In addition to the RDW, we found differences in clinical and biochemical parameters between surviving and non-surviving patients, such as age, chronic kidney disease, mechanical ventilation requirement, superinfection, initial oxygen saturation, creatinine, platelet and leukocyte count, prothrombin time, glucose, LDH, C-reactive protein (CRP), serum ferritin, and D-dimer; findings that are consistent with previous studies [29,30,31,32,33,34,35,36,37,38,39,40].