Outcomes in African-Americans vs. Caucasians using thymoglobulin or interleukin-2 receptor inhibitor induction: Analysis of USRDS database

Aim: We used the USRDS database to test the hypothesis that graft survival was similar using either rabbit antithymocyte globulin (rATG) vs. interleukin-2 receptor inhibitor (IL2i) in the Prograf era. We further explored the variable of race in the two groups of patients. Methods: We conducted a retrospective cohort study of kidney transplant patients in the USRDS from 2000 through 2005 to compare graft survival (including death) using rATG vs. IL2i with particular reference to outcomes between African-Americans vs. Caucasians. Kaplan-Meier analysis was performed to assess patient and graft survival after transplantation, stratified by recipient induction with rATG versus IL2i. Cox regression analysis was performed to assess adjusted survival after transplantation, assessing whether induction rATG (vs. IL2i) was significant as an interaction term (i.e. an effect modifier) with black race for graft survival. Propensity score analysis was used to address potential confounding by indication. Results: In stratified Cox Regression analysis limited to IL2i, black race was significantly associated with graft loss (adjusted hazard ratio (AHR) 1.17, 95% CI, 1.09-1.26). In analysis limited to rATG induction, black race was not significant (AHR 1.00, 95% CI, 0.92-1.10). We detected a significant interaction between rATG and black race (in comparison with non-black race) for the development of graft loss (AHR, 0.86, 95% CI, 0.76-0.97). Analysis limited to black recipients showed that while use of rATG was not significantly different from IL2i (AHR 0.95, 95% CI 0.87-1.04), the direction of this association was in the opposite direction of non-blacks. Conclusions: Patient and graft survival were similar in African-American and Caucasian recipients of kidney transplantation using either rATG or IL2i. Limitations of the study are the retrospective nature of USRDS data, center-bias in using rATG vs. IL2i and lack of data on steroid dosage. Results of the present study call for a critical review of induction practices.