Proximity to transplant center and outcome among liver transplant patients

Abstract

In the United States, distance from liver transplant center correlates with worsened outcomes; the effects of geography elsewhere are unassessed. We performed a national registry analysis of United Kingdom listings for liver transplantation (1995-2014) and assessed whether travel time to transplant center correlates with outcome. There were 11 188 listings assessed (8490 transplanted), with a median travel time to center of 60 minutes (range 36-86). Of the national population, 3.38 × 10⁷ (55.1%) reside ≥60 minutes from a center, and 7.65 × 10⁶ (12.5%) >119 minutes. After competing risk analysis, increasing travel time was associated with an increased risk of death after listing (subdistribution hazard ratios relative to <60 minutes of 1.33 for 60-119 and 1.27 for >119 minutes; P < 0.001) and reduced likelihood of transplantation or recovery (0.94 and 0.86; P < 0.001). Among those transplanted, travel time was not associated with retransplant-free survival (P = 0.532). We used our model to examine optimal placement of a new center and identify a single site with a total travel time reduction of ≈10%. Our findings of disparities in accessibility of liver transplantation showed worse outcomes following listing in those distant from their transplant center, and our description of a method to model a new center complement existing data and support similar analyses of other networks.

Keywords: business / management; clinical research / practice; disparities; health services and outcomes research; informatics; liver disease; liver transplantation / hepatology; organ transplantation in general; patient characteristics; patient referral.

Figure 1

Flowchart of exclusions. Adult patients (17 186) were listed for liver transplantation from 1995 to 2014 inclusive. After application of the exclusion criteria, an analysis cohort of 11 188 was generated

Figure 2

Geographic distribution of listings for liver transplantation. Geographic distribution of patients listed for liver transplantation in England, Scotland, and Wales 1995‐2014 inclusive after the exclusions detailed in Figure 1 [Color figure can be viewed at wileyonlinelibrary.com]

Figure 3

Listings for liver transplantation by postcode area. The number of listings for liver transplantation 1995‐2014 for each postcode area (n = 2736) was aggregated from the constituent postcode area and plotted against the 2011 National Census population. Confidence intervals at P = .05 and .002 were then generated to assess for those postcode areas contributing either more or fewer than expected listings. Those areas contributing fewer listings than expected at P < .002 are marked in blue; those contributing more at P < .002 are marked in red; text labels represent postcode areas. Postcode areas containing a liver transplant center (7) are plotted with a square rather than a circular marker [Color figure can be viewed at wileyonlinelibrary.com]

Figure 4

Travel time to nearest liver transplant center. A, Map of Great Britain showing the locations of current liver transplant centers (cyan circles), renal transplant centers without liver transplant capability (yellow circles), and calculated travel time to the nearest liver transplant center from each postcode district in 30‐minute intervals. B, Frequency distribution of travel time from postcode district of residence of patients listed for transplantation to the liver transplant center attended (n = 11 188). Red line denotes cumulative frequency. C, Frequency distribution of travel time from postcode district of residence of total resident population to the nearest liver transplant center (n = 6.13 × 10⁷). Red line denotes cumulative frequency [Color figure can be viewed at wileyonlinelibrary.com]

Figure 5

Outcome following listing for liver transplantation. A, Proportion of patients who had died following listing for liver transplantation categorized by travel time to listing transplant center (n = 11 188; P = .003 by log‐rank test). B, Proportion of patients who received transplantation or were removed from the waiting list because of an improvement in their clinical condition following listing for liver transplantation categorized by travel time to listing transplant center (n = 11 188; P = .005. by log‐rank test) [Color figure can be viewed at wileyonlinelibrary.com]

Figure 6

Modeled reductions in travel time by introduction of a new liver transplant center at various locations. The models described elsewhere in this document were repeated with the addition of a hypothetical new liver transplant center at each of 15 locations. The reduction in the number of minutes of traveling time for each listing for transplantation, or member of the population, to attend their nearest liver transplant center with and without the modeled new center was calculated. Panel A represents all listings for liver transplantation 1995‐2014 after the application of our exclusion criteria; Panel B represents all listings without exclusions; Panel C represents travel for the population of England, Scotland, and Wales as at the 2011 National Census; Panel D represents the same Census population but normalized to age‐adjusted standardized mortality rates (ASMR)