Increased urinary cystatin C reflects structural and functional renal tubular impairment independent of glomerular filtration rate

UcysC/Ucrea ≥ 11.3 mg/mmol is not an accurate marker to detect GFR ≤ 60 mL/min/1.73 m2, but reflects tubular dysfunction and proteinuria due to heavy proteinuria and tubulointerstitial disease.