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Published on: May 10, 2013
Cystatin C-based calculation of glomerular filtration rate in kidney transplant recipients
U Pöge1, T Gerhardt, B Stoffel-Wagner
1Department of Internal Medicine I, University of Bonn, Bonn, Germany. dr.poege@nephrologie-bonn.de
Insights
Cystatin C (Cys C) formulas show improved diagnostic accuracy for estimating glomerular filtration rate (GFR) in renal transplant patients compared to the MDRD formula. The Hoek and Larsson equations offer better precision and accuracy for GFR assessment post-transplant.
Area of Science:
- Nephrology
- Clinical Chemistry
- Transplantation Medicine
Background:
- Cystatin C (Cys C) is recognized as an alternative marker for assessing renal function.
- Estimating glomerular filtration rate (GFR) using Cys C has been underexplored, particularly in post-renal transplant (RTx) patients.
- Existing Cys C-based equations require validation in specific patient cohorts like those post-RTx.
Purpose of the Study:
- To evaluate the diagnostic accuracy of three Cystatin C-based GFR estimation formulas (Larsson, Hoek, Filler) in patients following renal transplantation.
- To compare the performance of these Cys C formulas against the established Modification of Diet in Renal Disease (MDRD) formula.
- To determine the clinical utility of Cys C for GFR calculation in the post-RTx setting.
Main Methods:
- A study involving 108 consecutive patients after renal transplantation.
- GFR was measured using technetium-diethylenetriamine pentaacetic acid ((99m)Tc-DTPA) clearance as the gold standard.
- Diagnostic accuracy of Larsson, Hoek, and Filler Cys C-based equations was compared with the MDRD formula.
Main Results:
- All calculated GFR estimates showed high correlation with true GFR, with no significant differences between formulas.
- The Hoek and Larsson Cys C equations demonstrated significantly better precision and accuracy (within 30% and 50% of true GFR) compared to the MDRD formula.
- The Hoek formula exhibited negligible bias and superior accuracy (97.2% within 50% of true GFR) compared to MDRD (85.3%).
Conclusions:
- Cystatin C-based GFR estimation formulas, particularly the Hoek and Larsson equations, offer superior diagnostic performance in renal transplant recipients.
- These Cys C formulas may be more reliable than traditional creatinine-based equations like MDRD for GFR assessment post-RTx.
- Cystatin C holds promise as a valuable tool for monitoring renal function after transplantation.
Abstract:
Cystatin C (Cys C) has been shown to be an alternative marker of renal function. However, estimation of the glomerular filtration rate (GFR) based on Cys C has received little attention. Recently, several Cys C-based equations were developed in different patient cohorts. To date, the benefit of a Cys C-based GFR calculation in patients after renal transplantation (RTx) remains to be elucidated. We compared the diagnostic accuracy of three Cys C-based formulae (Larsson, Hoek, Filler which used an immunonephelometric method) with the results of the Modification of Diet in Renal Disease (MDRD) formula. GFR was measured by means of technetium-diethylenetriamine pentaacetic acid ((99m)Tc-DTPA) clearance in 108 consecutive patients after RTx. Correlation coefficients of all calculated GFR estimates with the true GFR were high but did not differ significantly from one another (0.83-0.87). The MDRD and Filler equations overestimated GFR significantly, whereas the Larsson equation significantly underestimated GFR. Bias of the Hoek formula was negligible. Precision of the Hoek (8.9 ml/min/1.73 m(2)) and Larsson equations (9.6 ml/min/1.73 m(2)) were significantly better than MDRD equations (11.4 ml/min/1.73 m(2); P< or =0.035 each). Accuracy within 30% of real GFR was 67.0 and 65.1% for the MDRD and Filler formulae, and 77.1% for the Larsson and Hoek formulae, respectively. Accuracy within 50% of true GFR for the Hoek formula (97.2%) was better than for the MDRD equations (85.3%). Cys C-based formulae may provide a better diagnostic performance than creatinine-based equations in GFR calculation after RTx.
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