Cystatin C

Cystatin C is a protein produced by most cells in the body and filtered by the kidneys at a constant rate. Unlike creatinine, its levels are less affected by muscle mass or diet, making it potentially a more sensitive marker of early kidney dysfunction, especially when creatinine-based eGFR is borderline or muscle mass is atypical. Elevated levels indicate reduced glomerular filtration rate. Use eGFR calculated from Cystatin C (eGFRcys) or combined Creatinine-Cystatin C (eGFRcr-cys) for the best assessment of kidney function.