Cystatin C

Cystatin C is a protein produced at a steady rate by nearly all cells and filtered from the blood by the kidneys. Because it is generated at a constant rate and is less influenced by muscle mass, ethnicity, or diet, cystatin C provides a more accurate estimate of kidney health than creatinine in many cases. Elevated levels may indicate impaired kidney health and increasingly are used in conjunction with or as an alternative to creatinine-based eGFR calculations. In 2021, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) introduced new race-free eGFR equations incorporating cystatin C, creatinine, or both. These updated equations are endorsed by national bodies such as the American Society of Nephrology and the National Kidney Foundation and shown to be more accurate and generalizable across racial groups than previous race-based models. This shift reinforces cystatin C’s growing role in equitable kidney disease assessment and risk stratification. [65] [66]

[65]Delgado C, Baweja M, Crews DC, et al. A Unifying Approach for GFR Estimation: Recommendations of the NKF-ASN Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease. Am J Kidney Dis. 2022;79(2):268-288.e1. doi:10.1053/j.ajkd.2021.08.003

[66]Inker LA, Eneanya ND, Coresh J, et al. New Creatinine- and Cystatin C–Based Equations to Estimate GFR without Race. N Engl J Med. 2021;385(19):1737-1749. doi:10.1056/NEJMoa2102953