Accurate estimation of the glomerular filtration rate (GFR) is crucial for the management of kidney recipients, since it is the most predictive parameter of allograft failure that drives patient monitoring and decision-making. Standard and recent race-free GFR equations have been developed in native kidneys, but their performances in transplant kidney population remains unknown. We aimed at developing a kidney-transplant-specific GFR equation, and comparing its performance to standard GFR equations.

Historically, GFR equations, which predict the measured GFR (mGFR), were developed on patients with native kidneys and were further validated and used in kidney recipients. However, studies have shown significant heterogeneity in the performances of GFR equations when applied in kidney recipients, which may be attributed to variations and intrinsic characteristics specific to the transplant population. We thus made the hypothesis that GFR equations developed on a large, well-phenotyped kidney recipient cohort might achieve good performances in predicting mGFR.

The project therefore aims to:

1. Develop new kidney-recipient-specific (KRS) GFR equations and compare their performances with the standard GFR equations
2. Investigate whether the use of race increasers the performances of the new kidney-recipient-specific (KRS) GFR equations
3. Evaluate the effects of the new equations on the chronic kidney disease (CKD) prevalence and GFR stage

This study will provide us with data of kidney transplant patients that may allow the development of a new KRS GFR equation.

A new KRS GFR equation that presents with increased performances, as compared to current GFR equations, will improve the GFR calculation in kidney recipients, and therefore improve clinical decisions and the long-term kidney allograft management. Decisions regarding the return to dialysis or placement on the transplant waiting list will be taken with more accuracy and therefore potentially improve the financial allocation of kidney transplantation for the society.

Inclusion Criteria:

• Living or deceased donor kidney recipient transplanted between 01/01/2000 and 01/01/2021.
• Men or women over 18 years of age.
• Written informed consent at the time of transplantation for the center database.

Exclusion Criteria:

• Combined transplantation

The development cohort consisted of kidney transplant recipients from 3 centres in France. The validation cohorts consisted kidney transplant recipients from 6 centers in Europe and 1 in the Unites states.