IL6 and COVID-19: However, relative to COVID-19 severity, IL-6 saliva and plasma levels were associated with increased disease severity after adjusting for age, male sex, BMI, DM, and COVID-19 severity markers including D-dimer, CRP, and ferritin (Fig. 3F for plasma, P < 0.001; and Fig. 3G for saliva, Supplementary Table 3).