Published in: American Journal of Kidney Diseases (2014) vol. 64, iss. 5, pp. 817-820 Status: Postprint (Author’s version)
Creatinine-Based GFR Estimating Equations in Kidney Transplant
Recipients
Pierre Delanaye, MD, PhD
University of Liège- Liège, Belgium
To the Editor:
Shaffi et al1 conclude that the MDRD (Modification of Diet in Renal Disease) Study and CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equations perform better in kidney transplant recipients than all other proposed glomerular filtration rate (GFR) estimating equations, confirming data from White et al2 in 2008. We have 4 comments regarding this conclusion.
First, it is not surprising that equations developed with standardized serum creatinine level and validated against a "true" reference method (not creatinine clearance) perform better than others.
Second, we believe that the most important question in clinical practice is which of the 2 equations performs better in kidney transplant recipients. This question is examined only partially in the article, though a recent study3 showed that the MDRD Study equation outperforms the CKD-EPI equation in these patients.
Third, the authors evaluated the Berlin Initiative Study (BIS) equation in a cohort with a mean age of 54 years. This is questionable and unfair because the BIS equation was explicitly designed to estimate GFR in patients 70 years or older. These patients are poorly represented in the 5 cohorts studied; thus, the results of Shaffi et al unjustly discredit the BIS equation, which was developed with high-quality methodology4.
Fourth, the authors conclude that the MDRD Study and CKD-EPI equations can be used for clinical management However, we must keep in mind that these equations misestimate true GFR by > 30% in 1 of 5 patients. It is time to focus on these individuals. Further, in the context of kidney transplantation, we believe that measuring GFR is useful in both clinical practice and research.5
Acknowledgements
Financial Disclosure: The author declares that he has no relevant financial interests.
References
1. Shaffi K, Uhlig K, Perrone RD, et al. Performance of creatinine-based GFR estimating equations in solid-organ transplant recipients. Am J Kidney Dis. 2014;63(6):1007-1018.
2. White CA, Huang D, Akbari A, Garland J, Knoll GA. Performance of creatinine-based estimates of GFR in kidney transplant recipients: a systematic review. Am J Kidney Dis. 2008;51(6):1005-1015.
3. Masson I, Flamant M, Maillard N, et al. MDRD versus CKD-EPI equation to estimate glomerular filtration rate in kidney transplant recipients. Transplantation. 2013;95(10):1211-1217.
4. Schaeffner ES, Ebert N, Delanaye P, et al. Two novel equations to estimate kidney function in persons aged 70 years or older. Ann Intern Med. 2012;157(7):471-481.
5. Delanaye P, Mariat C. The applicability of eGFR equations to different populations. Nat Rev Nephrol. 2013;9(9):513-522.
