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Inaccuracy of GFR predictions by plasma cystatin C in patients without kidney dysfunction and in advanced kidney disease.

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Author

Summary, in English

BACKGROUND: In clinical practice there is need for a simple and reliable test for determination of impaired renal function. With reductions in GFR, the plasma cystatin C concentration (C, mg/l) will increase earlier than serum creatinine, and it is generally agreed that plasma cystatin C is only little affected by body weight, age or sex. However, some reports indicate that cystatin C may be influenced not only by GFR, but also by malignancy, inflammation and high doses of corticosteroids. The aim of the present study was to investigate how plasma cystatin C predicts GFR in distinct subcategories of patients with various disorders as well as in organ transplant patients. METHODS: Plasma cystatin C was measured in 536 patients (age range 0.3-96 years, 262 females, 274 males), consecutively referred to our hospital for determination of GFR by iohexol clearance. Correlations of log GFR vs. log cystatin C were used to compare plasma cystatin C and measured GFR for the following categories: individuals with no known kidney disease (No-KD), malignant patients with (mostly) normal GFR, solid organ-transplanted patients, and patients with native chronic kidney disease (CKD). RESULTS: In patients with normal kidney function and cystatin C level <or= 1 mg/l, the cystatin C was poorly correlated with GFR (R2=0.13). By contrast, in patients with chronic kidney disease (log) plasma cystatin C was highly correlated with (log) GFR (R2=0.87). This correlation was more or less unchanged whether the cause of the reduction in GFR was CKD at Stages 1-3 (90>GFR>30 ml/min(-1) (1.73 m2)(-1)) or solid organ transplantation (GFR=84.55 C(1.7666) and GFR=83.95(C-1.5968), respectively). CONCLUSION: Therefore, for these categories, a common equation for all patients with increased cystatin C, irrespective of cause of renal impairment, could be used, namely that presented by Grubb et al. [2005] (GFR=83.93(C-1.676)). However, at marked reductions of renal function (GFR<30 or cystatin C>2), i.e. for CKD Stages 4 and 5, the Grubb prediction equation is less accurate. Based on our data, we suggest the equation GFR=50.52 C(-1.26) for this category of patients.

Publishing year

2008

Language

English

Pages

331-338

Publication/Series

Clinical Nephrology

Volume

69

Issue

5

Document type

Journal article

Publisher

Dustri-Verlag

Topic

  • Urology and Nephrology

Status

Published

ISBN/ISSN/Other

  • ISSN: 0301-0430