Her cystatin C was 1.1 mg/L and calculated glomerular filtration rate was 56 mL/min/1.73 m2 (by CKiD U25 eGFR equation using creatinine and cystatin C), placing her in Stage 3 chronic renal failure (defined by a GFR between 30 and 59 mL/min/1.73 m2). Here, CST3 is linked to chronic kidney disease.