ABSTRACT: Background:Kidney transplant recipients are given induction therapy to rapidly reduce the immune response and prevent rejection. Guidelines recommend that an interleukin-2 receptor antibody (basiliximab) be the first-line agent and that a lymphocyte-depleting agent (antithymocyte globulin [ATG]) be reserved for those at high immunologic risk. Objective:To determine the incidence, risk factors, and outcomes for patients who receive both basiliximab and ATG for induction compared to either agent alone. Design:Retrospective cohort study. Setting:We used the transplant electronic medical record at the University of Alberta Hospital in Edmonton, Canada. Patients/samples/participants:We included incident adult kidney transplant recipients from 2013 to 2018. Measurements:We measured baseline characteristics, type, and dose of induction therapy used, estimated glomerular filtration rate (eGFR) at 1-year posttransplant, and outcomes of all-cause graft failure, death-censored graft failure, all-cause mortality, and death with a functioning graft. Methods:Differences between induction groups were compared using chi-square test for categorical variables and Kruskal-Wallis tests for continuous variables. We performed multivariable logistic regression modeling with type of induction therapy as the dependent variable and the case-level factors as the predictors (adjusted odds ratio). We estimated the Kaplan-Meier failure functions and used log-rank tests to assess statistical significance of differences in unadjusted incidence across induction therapy types. We compared cumulative incidence functions using a Fine and Gray competing risk regression model. Results:In all, 430 kidney transplant recipients were followed for a mean of 3.9 years (standard deviation 1.5). Of these, 71% (n = 305) received basiliximab alone, 22% (n = 93) received ATG alone, and 7% (n = 32) received both basiliximab and ATG. After adjusting for age and sex, compared to the basiliximab alone group, patients were more likely to receive dual-induction therapy if they were sensitized (calculated panel reactive antibody ?80%), had diabetes mellitus or peripheral vascular disease, or experienced delayed graft function. Compared to the ATG alone group, the dual-induction therapy group had worse graft function at 1 year (mean eGFR 42 vs. 59 mL/min/1.73 m2, P = .0008) and an increased risk of all-cause graft failure (31% vs. 13%, P = .02) and death-censored graft failure (16% vs. 4%, P = .03). Limitations:There is a risk of confounding by indication, as patients who received dual-induction therapy likely had worse outcomes due to the indication for dual-induction therapy (such as delayed graft function). Conclusions:In our study, 1 out of 10 recipients who were treated with basiliximab also received ATG for induction therapy. These patients experienced worse outcomes than those treated with ATG alone. Trial registration:Not applicable (cohort study).
