The new body mass index system in predicting renal graft outcomes

Obesity has been related to poor renal graft function. The aim of this study was to compare the long-term graft outcomes of living-related kidney recipients regarding donor-to-recipient body mass index (BMI) parameters using the old Quetelet BMI formula and the new Trefethen BMI formula.

From November 2002 to November 2010, 62 consecutive living-related kidney transplantations were reviewed retrospectively. Four donor-to-recipient BMI parameters were used: (1) BMI difference by the old formula, (2) BMI difference by the new formula, (3) BMI ratio by the old formula, and (4) BMI ratio by the new formula. Long-term outcomes, including graft survival (GS) and rejection-free graft survival (RFGS) either overall or at 5 years post-transplantation, were analysed according to these parameters.

The baseline demography was similar among tertiles according to the four BMI parameters tested. Although there is no significant difference in the long-term survivals by the old and new BMI formula, we found that the area under receiver operating characteristic (ROC) curve is larger using the new formula, either by BMI difference (0.584 vs 0.559 in 5-year GS and 0.658 vs 0.636 in 5-year RFGS) or by BMI ratio (0.584 vs 0.561 in 5-year GS and 0.644 vs 0.626 in 5-year RFGS). The same trend was observed in overall survival outcomes.

The new Trefethen BMI formula seems to predict long-term renal graft outcomes better than the old Quetelet BMI formula.