We employed propensity score stratification using the propensity function of Imai and van Dyk14 in order to estimate the effect of the treatment on critical illness in COVID-19 independent of the known risk factors for critical illness in COVID-19: age, sex, BMI, C-reactive protein (as a proxy for autoimmune disease), cystatin C (as a proxy for cardiovascular disease), alanine aminotransferase (as a proxy for chronic liver disease), and creatinine (as a proxy for chronic kidney disease). Here, CST3 is linked to COVID-19.