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Effect of regional competition on heart transplant waiting list outcomes
Vidang P Nguyen1, Raymond C Givens2, Richard K Cheng1
1Division of Cardiology, University of Washington, Seattle, Washington, USA.
Insights
Heart transplant urgency designations show varied risk rates. Increased competition between transplant centers is linked to differing outcomes for patients awaiting heart transplants, necessitating risk normalization strategies.
Area of Science:
- Cardiology
- Transplant Surgery
- Health Services Research
Background:
- Heart transplant urgency designations aim to standardize risk, but heterogeneity exists.
- Regional competition for donor organs may contribute to variations in patient outcomes.
- This study investigates the association between transplant center competition and outcome rate variations within urgency status designations.
Purpose of the Study:
- To assess if transplant center competition is associated with differing event rates within heart transplant urgency status designations.
- To determine the impact of market competition, quantified by the Herfindahl-Hirshman Index (HHI) and donor service area (DSA) density, on waiting list outcomes.
- To identify potential factors contributing to risk heterogeneity in heart transplant allocation.
Main Methods:
- Analysis of 20,237 adult heart transplant registrants listed between July 1, 2006, and July 1, 2013.
- Quantification of market competition using HHI and DSA density per million population.
- Application of Cox models to evaluate the association between competition metrics and waiting list outcomes (death or delisting as too ill) within specific status designations.
Main Results:
- Significant variation in outcome rates (death or delisting) was observed across centers for Status 1A, 1B, and 2 designations (p < 0.0001 for all).
- Increased market competition (lower HHI) was associated with differential outcome rates within higher urgency statuses: Status 1A (HR 0.94, p=0.012) and Status 1B (HR 0.95, p=0.010).
- Center density within the DSA did not show a significant association with outcome rates across status designations.
Conclusions:
- Outcome rates within heart transplant urgency designations vary significantly between centers.
- Transplant program competition partially explains this observed variation in risk.
- Further strategies are needed to normalize risk within heart transplant status designations to ensure equitable outcomes.
Background:
Heterogeneity of risk within heart transplant urgency designations is undesirable. Regional competition for donor hearts may contribute to this variation in risk. In this study we assessed whether an association exists between center competition and variation in event rates within status designations on the waiting list.
Methods:
Our study sample included 20,237 adult transplant registrants initially listed between July 1, 2006 and July 1, 2013. Market competition was quantified using the Herfindahl-Hirshman Index (HHI) and number of centers within a donor service area (DSA) per 1 million people. A Cox model was used to assess for variation in waiting list outcomes within status designation by both HHI and DSA density. The primary outcome was death or delisting as too ill.
Results:
Outcome rates within status designations differed significantly between centers: Status 1A, center p < 0.0001; Status 1B, center p < 0.0001; and Status 2, center p < 0.0001. Market competition (decreasing HHI) was associated with differential outcome rates within higher urgency status designation [Status 1A hazard ratio (HR) 0.94, p = 0.012; Status 1B HR 0.95, p = 0.010; and Status 2 HR 1.02, p = 0.360]. Center density within the DSA was not associated with outcome rates within each status designation (Status 1A HR 0.99, p = 0.961; Status 1B HR 1.03, p = 0.901; and Status 2 HR 1.20, p = 0.399).
Conclusions:
The rate of death or delisting as too ill within urgency designations varies between transplant centers and is partially explained by competition between transplant programs. Further methods of normalizing risk within status designations are necessary.
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