Appraisal of GFR-Estimating Equations Following Kidney Donation

Background It is not clear which serum creatinine–based glomerular filtration rate (GFR)-estimating model performs best in kidney donors. Study Design Study of diagnostic accuracy. Setting & Participants From a population of 3,698 kidney donors, 255 donors underwent iohexol GFR measurement (mGFR). Index Test (Intervention) mGFR by means of plasma disappearance of iohexol. Reference Test or Outcome GFR was estimated (eGFR) by using the Cockcroft-Gault equation (eGFRCG ), Mayo Clinic equation (eGFRMC ), and Modification of Diet in Renal Disease (MDRD) Study equation (eGFRMDRD ). Results Mean mGFR was 71.8 ± 11.8 mL/min/1.73 m2 , and 85.5% had mGFR greater than 60 mL/min/1.73 m2 . eGFRCG underestimated mGFR by 3.96 ± 13.3 mL/min/1.73 m2 and was within 30% of mGFR 89.4% of the time. eGFRMC overestimated mGFR by 8.44 ± 11.9 mL/min/1.73 m2 and was within 30% of mGFR in 83.1% of cases. eGFRMDRD underestimated mGFR by only 0.43 ± 11.7 mL/min/1.73 m2 , and the proportion within 30% of mGFR was greatest in the tested model; 94.1% of the time. However, eGFRMC was most accurate in classifying donors according to having eGFR less than 60 mL/min/1.73 m2. Limitations Lack of ethnic diversity and response bias. Conclusions The MDRD Study equation is least biased, and because it is routinely reported by most laboratories, it is the best readily available model for estimating GFR in kidney donors.