CST3 and chronic kidney disease: Furthermore, in patients with early-stage CKD (eGFR ≥30 mL/min/1.73 m2), cystatin C exhibited a stronger correlation with eGFRCr-Cys (R2 = 0.83) than in those with advanced disease (R2 = 0.70), suggesting its particular value in detecting mild renal impairment.