CRP and COVID-19: Based on a living systematic review, the 4C Mortality Score was developed and validated by Knight et al17 in derivation and validation cohorts of 35,463 and 22,361 patients, respectively, and has been identified as the most extensively validated and best model to predict in-hospital mortality in COVID-19 after 30 days.17, 18, 19 The 4C Mortality Score is a risk stratification score based on the following highly predictive clinical items; sex, age, number of comorbidities, vital signs, blood urea level, and C-reactive protein (CRP) level.