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.