IL6 and COVID-19: In the COVID-19 patients, the plasma sCD137 did not correlate with CRP (r = −0.231, p = 0.289), procalcitonin (r = 0.129, p = 0.559), ferritin (r = 0.208, p = 0.341), or IL-6 (r = −0.122, p = 0.600).