CYSTATIN C-BASED EQUATION (2012)

eGFR =
70.69 x (cysC)^-0.931

Abbreviations / Units

eGFR (estimated glomerular filtration rate) = mL/min/1.73 m²

cysC (cystatin C) = mg/L

Assays

• The cystatin-C based equation utilizes the Siemens (Date Behring) method and is not yet calibrated to IFCC standards. As a result, it may overestimate true GFR.
• To learn more, go to http://ckdepi.org/assays/cystatin-c/ or http://nkdep.nih.gov/lab-evaluation/cystatin-c.shtml.

Clinical Use

• For use in children 1-18 years old.
• May be useful as a confirmatory test in specific circumstances when eGFR based on serum creatinine is less accurate, or when the clinical scenario warrants a secondary test.
• May serve as a reasonable alternative to the multivariate cystatin C equation when there is a concern about one of the major variables (height, Scr, or cystatin C.)
• In most cases, the Bedside Schwartz equation [0.413*(ht/cm/Scr)] allows rapid and reasonably accurate estimation of GFR for clinical use in children with CKD. When measurement and calibration is more broadly available, GFR estimates using cystatin C may also have broad clinical utility.

References

1. Schwartz GJ, Schneider MF, Maier PS, et al. Improved equations estimating GFR in children with chronic kidney disease using an immunonephelometric determination of cystatin C. Kidney Int. 2012;82(4):445-453.
2. Grubb A, Blirup-Jensen S, Lindstrom V, Schmidt C, Althaus H, Zegers I. First certified reference material for cystatin C in human serum ERM-DA471/IFCC. Clin Chem Lab Med. 2010;48(11):1619-1621.