CST3 and chronic kidney disease: The first estimate is based on the serum creatinine level, while the second estimate is derived from serum cystatin C levels.5 It has been reported that the cystatin C-based renal function measurement is more accurate than the creatinine-based measurement in patients with mild or moderate CKD.6 However, it is unclear whether there is a difference between cystatin C- and creatinine-based renal function measurements in a general Japanese population.