Estimated glomerular filtration rate for longitudinal follow-up of living kidney donors

Background. Living kidney donor safety requires reliable long-term follow-up of renal function after donation. The current study aimed to define the precision and accuracy of post-donation estimated glomerular filtration rate (eGFR) slopes compared with measured GFR (mGFR) slopes. Methods. In 349 donors (age 51 +/- 10, 54% female), we analysed eGFR according to the 2009 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, Modification of Diet in Renal Disease (MDRD) and Cockcroft-Gault/body surface area (CG/BSA), creatinine clearance (CrCl) and mGFR (I-125-iothalamate) changes from 3 months until 5 years post-donation. Results. Donors had a pre-donation mGFR of 116 +/- 23 mL/min, at 3 months post-donation mGFR was 73 +/- 14 mL/min and at 5 years it was 79 +/- 16 mL/min. Between 3 months and 5 years post-donation, 28% of donors had a declining mGFR (-0.82 +/- 0.79 mL/min/year), 47% were stable and 25% had an increasing mGFR. Overall, eGFR equations showed good slope estimates (bias eGFR(CKD-EPI) 0.13 +/- 2.16 mL/min/year, eGFR(MDRD) 0.19 +/- 2.10 mL/min/year, eGFR(CG/BSA) -0.08 +/- 2.06 mL/min/year, CrCl -0.12 +/- 4.75 mL/min/year), but in donors with a decreasing mGFR the slope was underestimated (bias eGFR(CKD-EPI) 1.41 +/- 2.03 mL/min/year, eGFR(MDRD) 1.51 +/- 1.96 mL/min/year, eGFR(CG/BSA) 1.20 +/- 1.87 mL/min/ year). The CrCl had a high imprecision [bias interquartile range -1.51-3.41mL/min/year]. Conclusions. All eGFR equations underestimated GFR slopes in donors with a declining GFR between 3 months and 5 years post-donation. This study underlines the value of mGFR in the follow-up of donors with risk of progressive GFR loss.