Study Findings
This study confirmed that there is substantial variability in the utilization of induction therapy among US transplant centers. While this would ideally suggest that the highest utilization centers would have recipients with higher baseline risks for post-OHT rejection, instead we found there is a weak correlation between elevated baseline risk scores for rejection and the use of induction therapy. Furthermore, in an average center, induction therapy has no discernible impact on the odds of developing rejection requiring pharmacologic treatment within 1-year of OHT, where there is still a substantial proportion of variability among centers secondary to other unmeasured factors (VPC 17%). Instead, we found that HLA-mismatch, recipient age, recipient gender, ischemic cardiomyopathy, and unbalanced donor/recipient weight ratios were independent predictors of developing rejection within the first post-operative year. Likewise, the use of induction therapy did not have an impact on mortality at any follow-up interval among centers, although at the patient-level 30- and 90-day mortality was reduced in the induction therapy group. Another key finding was that patients who were more than 3 HLA-mismatched, gender mismatched, and black race, were more concentrated in centers with intermediate or high utilization rates of induction therapy. However, while these variables were statistically different among the utilization groups, the absolute magnitude of the differences were clinically nominal. In addition, taken as a composite assessment of rejection risk, there were no differences in composite risk scores for rejection across groups. As such, certain recipients may have received appropriately risk-stratification for induction therapy, yet with a weak correlation between the receipt of induction therapy and recipients at moderate and high pre-OHT baseline risks of rejection, further emphasis on overall, composite risk-stratification may be warranted during the pre-OHT evaluation. Additionally, we found that patients who received induction therapy tended to have higher rates of acute renal failure requiring dialysis, although this was not sustained at the center-level comparison. These findings may be less strongly associated with induction therapy itself and more likely to be associated with this subset of patients potentially being higher risk for renal failure pre-OHT and receiving induction therapy as a result.