Serum Cystatin C concentrations in particular were linked to COVID-19 mortality [21,24,26,27,28,29,35,36,39,42], severity [20,22,23,24,27,28,31,32,33,34,36,37,38,39,41,42,43,44], and the onset of acute kidney injury [29,30,35,40]. Here, CST3 is linked to COVID-19.