Pre- and postdonation bias as arithmetic (left) and relative values. Arithmetic bias was calculated as (mGFR − eGFR) and relative bias as [(mGFR − eGFR)/mGFR * 100]. Bias was divided according to tertiles of predonation mGFR/BSA; therefore, pre- and postdonation tertiles contain the same donors. Tertile median (IQR) values of predonation mGFR/BSA were 87 (82 to 92), 102 (99 to 106), and 118 (113 to 125), respectively. Corresponding values for postdonation mGFR/BSA were 56 (53 to 62), 66 (61 to 71), and 73 (68 to 77) ml/min per 1.73 m2. Bars represent medians with 95% confidence intervals. *P < 0.05 versus first tertile; #P < 0.05 versus second tertile.