Performance of the iBox Prognostication System in African American Kidney Transplant Recipients

Background: The iBox is a validated prognostication system that predicts long-term death-censored graft loss in kidney transplant recipients, but its performance in the specific population of African American recipients has not been fully studied. Methods: We conducted a multicenter study including 3,866 kidney transplant recipients from North America, of whom 1,040 (27%) were African American, to assess the impact of race on the iBox’s performance in predicting graft loss. Discrimination, calibration, overall fit and clinical utility were evaluated in the whole cohort and in African American and non-African American recipients. Results: Performance metrics for the prediction of graft loss were similar in both subgroups in terms of discrimination (c-index 0.80 [95% CI: 0.77-0.83] in African American recipients and 0.83 [95% CI: 0.81-0.85] in non-African American recipients, p=0.07), and observed/expected ratios (1.08 [95% CI: 0.95-1.23] and 0.99 [95% CI: 0.88-1.10], respectively, p=0.28). No significant interaction between iBox score values and race was found in multivariable analysis stratified by transplant center (p=0.29 for the interaction term). Results were consistent between subgroups regardless of the equation used to estimate glomerular filtration rate (Kidney Recipient Specific [KRS], CKD-EPI, or MDRD), with small variations in calibration across equations. Conclusions: The iBox prognostication system showed accurate discrimination, overall fit, and clinical utility up to 7 years post-risk evaluation in African American and non-African American kidney transplant recipients, supporting its robustness in this population.