CST3 and COVID-19: Cystatin C and its predictive function in terms of kidneys could also be used to predict other kidney diseases related to COVID-19 apart from AKI, although AKI as the most serious and fastest progressing one seems to be the most important–nevertheless, the ability to quickly test for levels Cystatin C among patients who have already left the hospital additionally emphasizes the role of this marker in terms of delayed complications of the disease [55].