The age-calibrated measured glomerular filtration rate improves living kidney donation selection process

Abstract

Recommendations on the glomerular filtration rate (GFR) threshold compatible with living kidney donation are not agreed upon. The recent KDIGO guidelines suggested a reset of the conventional cutoff value of 80 to 90 mL/min/1.73 m². While GFR physiologically declines with age, it is unclear whether and how age should be taken into account for selecting acceptable pre-donation GFR. In this multicenter retrospective study encompassing 2007 kidney donors in France, we evaluated the impact of age using two threshold measured GFR (mGFR)s (80 and 90 mL/min/1.73 m²). Three groups of donors were defined according to baseline mGFR: below 80, 80-89.9 and 90 mL/min/1.73 m² or more. Thirty-two percent of donors were selected despite an mGFR below 90 mL/min/1.73 m². Donors with the lowest mGFR were significantly older (60 ± 9 vs. 47 ± 11 years) and this applied to both male and female donors. The lifetime-standardized renal reserve, defined as the pre-donation mGFR value divided by the expected number of remaining years of life, was similar irrespective of baseline mGFR groups. Similar results were obtained when eGFR was used instead of mGFR. Finally, in a subgroup of 132 donors with repeated mGFR five years after donation, the magnitude of mGFR decrease was similar in all groups (-34.3%, -33.9%, and -34.9% respectively). Thus, the decision to accept individuals with mGFR lower than 90 mL/min/1.73 m² for kidney donation is highly dependent on the age of the candidate. Hence, threshold values lower than 90 mL/min/1.73 m² are reasonable for older donors. Age-calibrated mGFR may improve efficiency of the selection process.

Keywords: age; living kidney donors; measured GFR; threshold.