IL6 and COVID-19: Zeng et al. showed that a number of inflammatory markers of high sensitivity, such as serum soluble IL-2 receptor, IL-6, IL-8, IL-10, TNF-α, procalcitonin, ferritin, LDH, and CRP, together with the lymphocyte high-sensitivity PCR ratio, had very high levels in critically ill COVID-19 patients [29].