CRP and chronic kidney disease: With the aim of developing a more user-friendly application and according to the described methodology, we identified 7 variables present in all models with independent prognostic significance: peripheral blood oxygen saturation (SpO2)/fraction of inspired oxygen (FiO2) ratio, age, estimated glomerular filtration rate (calculated using Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI] equation), procalcitonin, C-reactive protein, updated Charlson comorbidity index (detailed in S2 Table) and lymphocytes.