Utility of the Japanese GFR estimation equation for evaluating potential donor kidney function

Background

In Japan, the number of living kidney transplantations has increased each year, and an accurate evaluation of renal function must be conducted before donation to minimize the risk to donors. Recently, the Japanese Society of Nephrology issued a new equation for estimating glomerular filtration rate (eGFR) in Japanese people. This study compared the accuracy of eGFR and creatinine clearance (Ccr) values with that of inulin clearance (Cin) for assessing renal function in kidney donors.

Methods

Clinical data were analyzed for 85 potential living kidney donors who had undergone routine measured GFR (mGFR) and Ccr measurements from October 2006 to November 2008 at a single center. Inulin clearance, representing the mGFR, was determined by standard method. The eGFR was calculated as: eGFR = 194 × Scr^?1.094 × Age^?0.287 (for females, ×0.739).

Results

Mean mGFR was 96.1 ± 14.7 (range 67.8–126.8); mean eGFR, 72.6 ± 12.7 (range 50.1–107.1); and mean Ccr, 117.3 ± 22.4 (range 35.1–170.1), in units of ml/min/1.73 m² for each. Relative to mGFR, the correlation coefficient for Ccr was 0.496, and the mean difference between the two values was 21.1 ml/min/1.73 m² (23.2%), with a root-mean square error (RMSE) of 19.6. The correlation coefficient between eGFR and mGFR was 0.502, and the mean difference between the two values was ?23.5 (23.7%), with a RMSE of 11.0. Bland–Altman plots showed that Ccr overestimated mGFR in 90.6% of cases, whereas eGFR underestimated mGFR in 95.3% of cases.

Conclusion

Ccr and eGFR values did not accurately estimate mGFR in Japanese living kidney donors.