Performance of the Japanese GFR equation in potential kidney donors

Background Japanese GFR equation was developed from mainly chronic kidney disease (CKD) subjects. Only a small number of healthy subjects were included in the development and validation of the GFR equation. We assessed the performance of the equation in potential kidney donors. Methods A total of 113 potential kidney donors was included. The data of CKD subjects that were previously reported were also included for comparison. GFR (mGFR) was measured by inulin clearance. The estimated GFR (eGFR) was calculated by the Japanese GFR equation. Bias of the equation (eGFR-mGFR) and urinary creatinine excretion were evaluated. Results There was no significant difference between eGFR and mGFR in 340 CKD subjects (54.2 ± 31.6 and 55.7 ± 33.2 ml/min/1.73 m2, respectively). Contrarily, the eGFR was significantly lower than mGFR in 113 potential kidney donors (78.9 ± 16.2 and 93.6 ± 19.2 ml/min/ 1.73 m2, respectively). The biases in potential kidney donors with eGFR 30-59 and 60-89 ml/min/1.73 m2 were significantly greater than those in CKD subjects (-19.2 ± 12.2 and-18.3 ± 16.4 ml/min/1.73 m2 in potential kidney donors and-3.8 ± 15.6 and-3.4 ± 17.6 ml/min/1.73 m2 in CKD subjects, respectively). Creatinine excretion per body weight of potential kidney donors was significantly higher than that of CKD subjects, suggesting higher creatinine generation in potential kidney donors. Conclusion The Japanese GFR equation underestimated GFR in potential kidney donors. Higher creatinine generation compared with CKD subjects may contribute to the underestimation of GFR by the Japanese GFR equation in potential kidney donors.