title: Effect of regional competition on heart transplant waiting list outcomes.
abstract: 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.
  
  
  
  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.
  
  
  
  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).
  
  
  
  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.
authors.affiliation: Division of Cardiology, University of Washington, Seattle, Washington, USA.
authors.forename: Vidang P
authors.initials: VP
authors.lastname: Nguyen
authors.affiliation: Division of Cardiothoracic Surgery, University of Washington, Seattle, Washington, USA.
authors.forename: Raymond C
authors.initials: RC
authors.lastname: Givens
authors.affiliation: Division of Cardiology, University of Washington, Seattle, Washington, USA.
authors.forename: Richard K
authors.initials: RK
authors.lastname: Cheng
authors.affiliation: Division of Cardiothoracic Surgery, University of Washington, Seattle, Washington, USA.
authors.forename: Nahush A
authors.initials: NA
authors.lastname: Mokadam
authors.affiliation: Division of Cardiology, University of Washington, Seattle, Washington, USA.
authors.forename: Wayne C
authors.initials: WC
authors.lastname: Levy
authors.affiliation: Division of Cardiology, University of Washington, Seattle, Washington, USA.
authors.forename: April
authors.initials: A
authors.lastname: Stempien-Otero
authors.affiliation: Division of Cardiology, Columbia University Medical Center, New York, New York, USA.
authors.forename: P Christian
authors.initials: PC
authors.lastname: Schulze
authors.affiliation: Division of Cardiology, University of Washington, Seattle, Washington, USA. Electronic address: tdardas@uw.edu.
authors.forename: Todd F
authors.initials: TF
authors.lastname: Dardas
mesh_terms: D016027:Heart Transplantation; D006801:Humans; D016016:Proportional Hazards Models; D014019:Tissue Donors; D014850:Waiting Lists
keywords: adult; allocation policy; health services; heart allocation; heart transplant