Do We Need a New Creatinine-Based Estimated GFR Equation for Kidney Transplant Recipients?

GFR is used for many critical decisions in all patients with kidney disease. In kidney transplant recipients, such decisions may be more frequent and more consequential and time sensitive, including detection of decreased kidney perfusion, obstruction of the urinary tract, consideration of biopsy, selection and dosage of immunosuppressive and antimicrobial agents, and use of contrast imaging. For the general population, current guidelines recommend estimated glomerular filtration rate (eGFR) using serum creatinine (eGFRcr) as the first step in GFR evaluation, with use of eGFR using cystatin C with or without creatinine (eGFRcr-cys or eGFRcys, respectively) or measured GFR (mGFR) as supportive tests. 1 Kidney Disease: Improving Global Outcomes (KDIGO)KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int Suppl. 2013; 3: 1-150https://doi.org/10.1038/kisup.2012.73 Abstract Full Text Full Text PDF Scopus (1779) Google Scholar ,2 Eckardt K.U. Delgado C. Heerspink H.J.L. et al. Trends and perspectives for improving quality of chronic kidney disease care: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference. Kidney international. 2023; https://doi.org/10.1016/j.kint.2023.05.013 Abstract Full Text Full Text PDF Scopus (0) Google Scholar A recent article by Raynaud et al. 3 Raynaud M. Al-Awadhi S. Juric I. et al. Race-free estimated glomerular filtration rate equation in kidney transplant recipients: development and validation study. BMJ. 2023; 381e073654https://doi.org/10.1136/bmj-2022-073654 Crossref Scopus (1) Google Scholar described the development and validation of a new eGFRcr equation in kidney transplant recipients, which the authors compared to the currently recommended eGFRcr equations by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI 2021 AS, recommended for use in the United States, and CKD-EPI 2009 ASR-NB, recommended for use in European countries). 4 Inker L.A. Eneanya N.D. Coresh J. et al. New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race. The New England journal of medicine. 2021; 385: 1737-1749https://doi.org/10.1056/NEJMoa2102953 Crossref PubMed Scopus (750) Google Scholar , 5 Delgado C. Baweja M. Crews D.C. et al. A Unifying Approach for GFR Estimation: Recommendations of the NKF-ASN Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease. J Am Soc Nephrol. 2021; 32: 2994-3015https://doi.org/10.1681/asn.2021070988 Crossref PubMed Scopus (0) Google Scholar , 6 Gansevoort R.T. Anders H.-J. Cozzolino M. et al. What should European nephrology do with the new CKD-EPI equation?. Nephrology Dialysis Transplantation. 2022; 38: 1-6https://doi.org/10.1093/ndt/gfac254 Crossref Scopus (12) Google Scholar , 7 Delanaye P, Schaeffner E, Cozzolino M, et al. The new, race-free, Chronic Kidney Disease Epidemiology Consortium (CKD-EPI) equation to estimate glomerular filtration rate: is it applicable in Europe? A position statement by the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM). Clinical chemistry and laboratory medicine. 2022. doi:10.1515/cclm-2022-0928. Google Scholar In this editorial, we describe the authors’ findings, interpret them in the context of the rationale and use of disease-specific eGFRcr equations, and conclude with our opinion about the next steps for improving GFR evaluation in kidney transplant recipients.