210
Views
137
CrossRef citations to date
0
Altmetric
Original Article

Determination of the production rate and non‐renal clearance of cystatin C and estimation of the glomerular filtration rate from the serum concentration of cystatin C in humans

, &
Pages 111-124 | Received 30 Jun 2004, Accepted 05 Nov 2004, Published online: 08 Jul 2009
 

Abstract

Cystatin C has been proposed as an endogenous marker for measuring glomerular filtration rate (GFR) and is regarded as being equivalent to or better than creatinine. However, there are no published data on the production rate (Cyspr) or on the non‐renal clearance of cystatin C (CLnr) in humans, which are essential parameters for GFR calculation. GFR was determined by measuring the plasma clearance of iohexol. Cystatin C, creatinine, urea and albumin were determined on the same serum samples as iohexol; 381 patients with a GFR range of 12–151 ml/min/1.73 m2, and 70 patients on haemodialysis were evaluated. Renal clearance of cystatin C (CLr) equals GFR * S (the sieving coefficient). Plasma clearance (CL) = CLr+CLnr. The relationship between Cyspr and the elimination rate (CL * serum‐cystatin C) can be expressed as Cyspr = (S * GFR+CLnr) * serum‐cystatin C. Assuming that the unknown values of Cyspr and CLnr are independent of GFR, the equation can be solved from GFR (iohexol clearance) and serum cystatin C (s‐Cys) patient data. For S = 1, we found Cyspr = 0.124±0.023 mg/min/1.73 m2 and Clnr = 22.3 ml/min/1.73 m2. For S = 0.94, found in rats, the values will be Cyspr = 0.117 mg/min/1.73 m2 and Clnr = 21 ml/min/1.73 m2 and S‐Cys in 70 patients on chronic haemodialysis was found to be 5.74±1.15 mg/l, in agreement with a calculated value of 5.56 mg/l (s‐Cys = 124/22.3) for GFR = zero. The mean value of the calculated Clnr for the 70 patients was 22.7±6.6 ml/min/1.73 m2, which confirms the calculated level and indicates its biological variation. We thus propose the following formula for calculating GFR using the values found for CLnr and Cyspr in this study: GFR = 124/s‐Cys−22.3 ml/min/1.73 m2, where serum cystatin C concentration is given as mg/l.

Reprints and Corporate Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

To request a reprint or corporate permissions for this article, please click on the relevant link below:

Academic Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

Obtain permissions instantly via Rightslink by clicking on the button below:

If you are unable to obtain permissions via Rightslink, please complete and submit this Permissions form. For more information, please visit our Permissions help page.