CST3 and Renal insufficiency: Using a combination of the serum creatinine and cystatin C levels (eGFRscr_cys) could improve the bias (−0.3 for eGFRscr_cys) of the equation and achieve the highest diagnostic accuracy for renal insufficiency (AUC60, 0.953; P < 0.05, except for eGFR_MDRD).