IL6 and COVID-19: CRP was chosen as the biomarker for inflammation in this study since it is widely used and affordable worldwide, it is correlated with serum IL-6 concentrations, and early clinical studies of COVID-19 had reported it to be associated with severity and prognosis, with a value of greater than 50 mg/L associated with severe disease and a concentration of around 75 mg/L distinguishing fatal from non-fatal cases.23, 24, 25, 26, 27, 28 Whether hypoxic patients with a CRP of less than 75 mg/L could benefit from tocilizumab is unknown.