Based on a comprehensive analysis comparing the first six months after implementation with the previous 18 months, the new kidney allocation system (KAS) is achieving its goals in many ways. This six-month analysis was performed on behalf of the OPTN Kidney Transplantation Committee and contains additional metrics beyond those included in previous reports. View more details on the analysis.
Trends from the first six months (through May 2015) include the following:
- Transplants have increased for the most difficult-to-match patients, those with a very high calculated panel reactive antibody (CPRA) indicating they are highly immunosensitized to most kidney offers. While transplants have increased six-fold for recipients with a CPRA of 99 to 100 percent, the trend in transplants for these patients has begun to decrease over the first six months, most likely reflecting a diminishing bolus effect.
- Transplants have increased substantially for patients with five or more years on chronic maintenance dialysis, owing to the back-dating of dialysis time for determining waiting time points under KAS.
- Transplants have increased for African-Americans, who tend to stay disproportionately longer on dialysis prior to being listed for a transplant. African-Americans are also more likely to have blood type B compared to other candidates, so the four-fold increase in the number of A2/A2BB transplants may also be contributing to this population’s increased access. However, only 3% of blood type B patients have been listed as eligible for these subtype-compatible kidneys, suggesting further growth in this area may be attainable.
- Due to the longevity matching component of KAS, fewer transplants are occurring in which the kidney is predicted to outlive the recipient. Prior to KAS, 14 percent of kidneys expected to last the longest (with a Kidney Donor Profile Index [KDPI] of zero to 20 percent) went to recipients age 65 or older, but this dropped to 5 percent post-KAS. While transplants have declined for patients in the 50-64 and 65 and older age groups, over half of all deceased donor kidney transplants under KAS are age 50 or older
- Transplants to pediatric patients (age 0-17) declined from 4.3 percent to 3.6 percent in the first six months; however, this difference is not statistically significant. Pediatric recipients are more often receiving kidneys expected to last longer (lower KDPI) under KAS compared to previously.
- Access to transplantation, as measured by transplant rates, for the small number of prior living donors that are registered on the waiting list has not changed statistically and remains sharply higher than for all other subpopulations. The number of deceased donor kidneys being recovered for transplantation per month has increased by about four percent. Transplant volume was up one percent. However, an initial rise in the kidney discard rate (from 18.5 to 20.2 percent) precluded even further increases in transplants under the new system. Utilization of high KDPI kidneys, in particular, did not improve in the early post-KAS period, as discard rates rose for these kidneys.
- More kidneys are now being shared across donor service area (DSA) boundaries. Previously about 20 percent of kidneys were transplanted outside of the recovering OPO’s DSA, and this has increased to about 33 percent under KAS. This increase in shipping, which is driven by both the regional and national distribution of kidneys for CPRA 99-100 percent patients as well as the combined local/regional distribution of high KDPI kidneys, has led to a rise in the average cold ischemic time (CIT) among transplanted kidneys. Pre-KAS, 18 percent of kidneys had 24 or more hours of CIT, whereas after KAS this has risen to 22 percent.
- The percentage of transplant recipients experiencing delayed graft function (DGF) has risen from 25 percent to 31 percent, likely owing to a variety of factors. These early increases in CIT and DGF may, however, resolve as bolus effects become smaller over time.
- Increased shipping has also amplified logistical challenges faced by OPOs trying to allocate kidneys regionally or nationally to very highly sensitized patients while reducing the risk of a positive crossmatch and the need for reallocation or organ discard. Establishing effective transplant center and OPO practices in this area is a vital, active topic of discussion within the Kidney Transplantation Committee and the transplant community at large.
KAS Trend Update — through September 2015
Several encouraging trends have been observed in months 7-10 (June – September, 2015):
- The number of deceased donor kidneys recovered for transplantation has increased sharply (a 9.6 percent increase compared to pre-KAS), as has the number of deceased donor kidney transplants (also a 9.6 percent increase). The kidney discard rate has returned to pre-KAS levels, dropping from 20.2 percent in the first six months to 18.4 percent in months 7-10. This more recent rate essentially mirrors the 18.5 percent rate in the 18 months before KAS. Discard rates also returned to pre-KAS levels for kidneys with a KDPI between 86 and 100 percent.
- Pediatric transplant volume increased in months 7-10. During this time, 4.2 percent of transplants went to recipients age 17 or younger, very similar to the 4.3 percent observed in the pre-KAS period. These recent trends suggest that any initial impact of KAS on pediatric access to transplantation was small and appears to have waned as bolus effects decrease.
- After increasing sharply from 31.5 percent to 37.9 percent in the first six months, the percentage of transplants to African Americans tempered somewhat to 35.2 percent in months 7-10, likely due to diminishing bolus effects related to the awarding of waiting time priority based on the candidate’s dialysis start date.
- Although many more candidates with a CPRA score of 99 to 100 percent are still receiving transplants compared to before KAS, their percentage dropped from 15 percent of transplants in the first six months to 12 percent in months 7-10.
- The rate of kidneys shipped outside the recovering OPO’s DSA decreased slightly to 31 percent.
These recent findings are based on limited data. They must be interpreted cautiously and further tracked to assess whether observed trends will be sustained.