An Updated Estimate of Posttransplant Survival After Implementation of the New Donor Heart Allocation Policy

Kevin A. Lazenby; Nikhil Narang; Kenley M. Pelzer; Gege Ran; William F. Parker

Disclosures

American Journal of Transplantation. 2022;22(6):1683-1690. 

In This Article

Abstract and Introduction

Abstract

The Organ Procurement and Transplant Network (OPTN) implemented a new heart allocation policy on October 18, 2018. Published estimates of lower posttransplant survival under the new policy in cohorts with limited follow-up may be biased by informative censoring. Using the Scientific Registry of Transplant Recipients, we used the Kaplan–Meier method to estimate 1-year posttransplant survival for pre-policy (November 1, 2016, to October 31, 2017) and post-policy cohorts (November 1, 2018, to October 31, 2019) with follow-up through March 2, 2021. We adjusted for changes in recipient population over time with a multivariable Cox proportional hazards model. To demonstrate the effect of inadequate follow-up on post-policy survival estimates, we repeated the analysis but only included follow-up through October 31, 2019. Transplant programs transplanted 2594 patients in the pre-policy cohort and 2761 patients in the post-policy cohort. With follow-up through March 2, 2021, unadjusted 1-year posttransplant survival was 90.6% (89.5%–91.8%) in the pre-policy cohort and 90.8% (89.7%–91.9%) in the post-policy cohort (adjusted HR = 0.93 [0.77–1.12]). Ignoring follow-up after October 31, 2019, the post-policy estimate was biased downward (1-year: 82.2%). When estimated with adequate follow-up, 1-year posttransplant survival under the new heart allocation policy was not significantly different.

Introduction

The Organ Procurement and Transplantation Network (OPTN) implemented a new donor heart allocation policy on October 18, 2018. Studies evaluating the impact of this new policy on posttransplant survival contain discrepant findings.[1] Five reports found decreased posttransplant survival under the new policy,[2–6] and two reports found no difference in posttransplant survival.[7,8] Notably, the studies with lower estimates of posttransplant survival in the post-policy era have significantly fewer follow-up observations of post-policy recipients compared with the studies finding unchanged survival.

One proposed explanation for the conflicting results is informative censoring bias.[9] A fundamental assumption of the Kaplan–Meier survival estimator is that censoring is statistically independent of survival time.[10] If censored patients have longer survival times than non-censored patients, the Kaplan–Meier estimator can be biased downward. Transplant programs are required to report recipient deaths faster than routine follow-up appointments for healthy recipients.[11] If a study's data are heavily censored, this differential data submission requirement based on recipient survival status could lead to a lower Kaplan–Meier estimate than the true population survival rate. Studies that reported lower estimates of posttransplant survival in the post-policy era[2–6] have significantly more censoring in their post-policy cohorts than the studies finding unchanged survival.[7,8]

This study uses more complete recipient follow-up data to evaluate the hypothesis that informative censoring biased the estimates of lower posttransplant survival in the new heart allocation system.

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