Background: The number of candidates on the kidney (KI) wait list (WL) abruptly flattened around the time the new Kidney Allocation System (KAS) was implemented (12/4/14). This is noteworthy as the WL has historically increased monotonically. We aimed to understand the drivers behind this, including changes in WL additions (add) and removals (rem).

Data and Methods: The cumulative size of the KI WL, as well as the monthly add and rem, were examined from 1/31/00 to 10/31/15. Trend lines were fit via piecewise linear regression to determine time trends, with the slope-change point determined algorithmically from the data.

Results: Figure 1 shows the trend in the WL, add, and rem by month. The KI WL plateaued shortly after KAS implementation, with add decreasing and rem increasing concurrently. The cumulative size of the WL saw an abrupt slope change around 12/21/14 (p<.0001, 95% CI=9/15/14-3/28/15) from 363 registrations (reg)/month to -75 reg/month, a 438 reg/month net decrease. The slope change was statistically significant (sig) (p<.0001). The post-KAS slope was not sig different from zero (p=0.2211), reflecting a plateauing of the WL. Both add and rem saw sig slope changes (p=0.0012, p=0.0167) around 12/21/14, with add decreasing by a net of 27 reg/month and rem increasing by a net of 30 reg/month; both were sig different from zero (p=0.0103, p=0.0016).

Figure 2 shows that fewer dialysis candidates were added to the KI WL post-KAS. An examination of rem reason trends shows that 'unable to contact candidate' increased by 23% in the 6 months pre- vs. post-KAS.

Conclusion: There has been a decrease in the growth and an unprecedented plateauing of the KI WL shortly after KAS implementation, due primarily to fewer candidate additions and more removals. In response to KAS, it appears that centers have changed list management practices and are waiting until dialysis time accumulates to list patients.

CITATION INFORMATION: Wilk A, Stewart D, Edwards E. Understanding the Dynamics of a Suddenly Plateauing Kidney Waiting List. Am J Transplant. 2016;16 (suppl 3).

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