After the publication by Trimarchi et al. and Shlipak et al. in which GFR was assessed by several methods in a multicenter study with 1119 subjects employing urinary clearance of iothalamate as the gold standard, including creatinine, cystatin C or combined CKD-EPI formulas, showing that the combined CKD-EPI equation was superior to equations based on either creatinine or cystatin C markers alone, we decided to consider cystatin C and the combined CKD-EPI equations to our previous available data [6, 20]. The gene discussed is CST3; the disease is chronic kidney disease.