CYSTATIN GFR

Serum creatinine has a drawback in the measurement of glomerular filtration rate (GFR) in that it may vary according to muscle mass. Cystatin C is a 13 kilodalton protein that is filtered by the glomerulus and reabsorbed and metabolized by tubular cells. The amount that is excreted into the urine is negligible. Its production is very steady, and not dependent on muscle mass. It has been proposed as an alterate marker Ifor estimating GFR. (coresh)

The literature is emerging, and showing that it has a benefit as a marker. Here are two formulae that might be useful in demonstrating the relationships between serum creatinine and serum cystatin C in adults. A Pediatric Cystatin GFR for Dako has been evaluated by Schwartz, et al (5)

CYSTATIN FORMULA

DADE (chemiluminescence) ADULT GFR = 77.24 X cys -1.2623
DADE (chemiluminescence) ADULT GFR (EPI) = 76.24 X cys -1.19
DAKO (immunoassay) ADULT GFR =99.43 X cys -1.5837
DAKO PEDIATRIC FORMULA USED:

GFR (ml/min per 1.73 m2)=39.1[height (m)/Scr (mg/dl)]0.516 * [1.8/cys (mg/L)]0.294[30/BUN (mg/dl)]0.169[1.099]male[height (m)/1.4]0.188.

cys = serum cystatin c (in mg/L)

CYSTATIN REFERENCES

  1. Dade-Behring Assay from Siemens
  2. Dako Control set
  3. Stevens LA, Padala S, Levey AS. Advances in glomerular filtration rate-estimating equations. Curr Opin Nephrol Hypertens. 2010 May;19(3):298-307.
  4. Stevens LA, Coresh J, Schmid CH, Feldman HI, Froissart M, Kusek J, Rossert J, Van Lente F, Bruce RD 3rd, Zhang YL, Greene T, Levey AS. Estimating GFR using serum cystatin C alone and in combination with serum creatinine: a pooled analysis of 3,418 individuals with CKD. Am J Kidney Dis. 2008 Mar;51(3):395-406
  5. Cystatin Children's GFR Calculator
  6. Schwartz, GJ, Munoz, A, Schneider, MF, Mak, RH, Kaskel, F, Warady, BA & Furth, SL: New Equations to Estimate GFR in Children with CKD. J Am Soc Nephrol:ASN.2008030287, 2009.
  7. Larsson A, Malm J, Grubb A, Hansson LO. Calculation of glomerular filtration rate expressed in mL/min from plasma cystatin C values in mg/L. Scand J Clin Lab Invest. 2004;64(1):25-30.
  8. Menon V, Shlipak MG, Wang X, Coresh J, Greene T, Stevens L, Kusek JW, Beck GJ, Collins AJ, Levey AS, Sarnak MJ.Cystatin C as a risk factor for outcomes in chronic kidney disease.Ann Intern Med. 2007 Jul 3;147(1):19-27.
  9. Stevens, LA, Coresh, J, Schmid, CH, et al. Estimating GFR using serum cystatin C alone and in combination with serum creatinine: a pooled analysis of 3,418 individuals with CKD.Am J Kidney Dis. 2008; 51(3):395-406

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