When we compared the concordance of CKD stages classified by various cystatin C equations versus CKD-EPI creatinine 2009 equation (Table 4(a)), the concordance was the highest with the average of creatinine 2009 and cystatin C 2012 (78.1%), followed by creatinine-cystatin C 2012—age, sex, and race (77.3%), and was the lowest with the spline Log cystatin C—age, sex, and weight (59.3%). Here, CST3 is linked to chronic kidney disease.