Cystatin C for Monitoring Kidney Health

Although the level of creatinine in the blood is often used to estimate the glomerular filtration rate (eGFR) -- and thereby kidney health -- creatinine may not always be the ideal substance to use for this purpose.

Creatinine is produced when muscle cells break down, therefore, creatinine levels are dependant on the amount of muscle in the body. Also, creatinine and eGFR calculations can be affected by other factors such as posture, thyroid disease, pregnancy, exercise, blood sugar levels and so on. As a result, researchers have sought another substance with levels that are more stable in the blood, which can be used to estimate eGFR. That substance may be cystatin C.

About Cystatin C

Cystatin C is a protein produced by many of the body's cells. It helps to protect connective tissue from breaking down and may help protect the body from infection.

Under normal conditions, cystatin C levels in the blood are relatively stable, particularly under conditions where creatinine is not. Moreover, cystatin C may be particularly useful in attempting to assess cases of early or subtle kidney damage when using creatinine levels cannot reveal this damage.

Cystatin C may also have other uses -- high levels of this protein in the blood have been linked to an increased risk of stroke, heart attack and death. This is because high cystatin C levels suggest that inflammation is taking place, inflammation that can damage whole organ-systems.

Cystatin C measurements may have multiple potential uses, but in this issue of TreatmentUpdate we focus on its use for estimating GFR.

References

1. Banfi G, Del Fabbro M, Lippi G. Serum creatinine concentration and creatinine-based estimation of glomerular filtration rate in athletes. SportsMedicine. 2009;39(4):331-7.
2. Bobek LA and Levine MJ. Cystatins -- inhibitors of cysteine proteinases. Critical Reviews in Oral Biology and Medicine. 1992;3(4):307-32.
3. Myers GL, Miller WG, Coresh J, et al. Recommendations for improving serum creatinine measurement: a report from the Laboratory Working Group of the National Kidney Disease Education Program. Clinical Chemistry. 2006 Jan;52(1):5-18.
4. Randers E, Erlandsen EJ. Serum cystatin C as an endogenous marker of the renal function -- a review. Clinical Chemistry and Laboratory Medicine. 1999 Apr;37(4):389-95.

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