OPTN/SRTR 2020 Annual Data Report: Living Donor Collective

The first successful solid organ transplant was a living donor kidney transplant in 1954. Since then, living donation has been an important source of organs for kidney and liver transplants in the United States. Unfortunately, the demand for organs has not kept pace with the supply, and unlike deceased donor transplant, there has been little growth in the number of living donor transplants over the past decade. To better understand possible barriers to living donation and long-term risks attributable to donation, the Health Resources and Services Administration (HRSA) directed the Scientific Registry of Transplant Recipients (SRTR) to establish a national registry of all living donor candidates and donors evaluated at US transplant programs to acquire lifetime follow-up information. Other goals include understanding the factors associated with candidate approval and variation in approval practices across centers. A pilot program was conducted from June 2018 through September 2020 to inform baseline data collection and registration processes. In September 2020, the registry began recruiting additional sites evaluating candidates for living donation. Here, we describe candidates registered at participating living donor kidney and liver programs, from June 2018 through the end of 2020. Not all programs submitted data throughout the whole period. Data for kidney and liver living donor candidates are presented separately.

OPTN/SRTR 2020 Annual Data Report: VCA.

The first vascularized composite allograft (VCA) transplant in the United States was performed in 1998 in a 40-year-old man who received a laryn-geal transplant after experiencing severe trauma to the throat 20 years before. The following VCA was a hand transplant in 1999 in a 37-year-old man who lost his left hand 13 years before. Since then, the field of VCA transplantation has made significant strides. On July 3, 2014, the Or gan Procurement and Transplantation Network (OPTN)/United Network for Organ Sharing (UNOS) oversight of VCA procurement and transplant in the United States went into effect. In the last decade, the number of candidates listed for and transplanted with VCA has increased. While patient demographic data, whether listed candidates or patients undergoing VCA transplant, is limited by sample size, the trend is a predominance toward a young/middle-aged, White population. Overall outcomes data have been promising, with the vast majority of VCA transplants resulting in functioning grafts.

OPTN/SRTR 2019 Annual Data Report: Pancreas.

The overall number of pancreas transplants decreased slightly, from 1027 in 2018 to 1015, in 2019, up from a nadir of 947 in 2015. However, the number of simultaneous pancreas-kidney transplants (SPKs) increased in 2019, with a corresponding drop in pancreas-after-kidney transplants (PAKs) and pancreas transplants alone (PTAs). New waitlist registrations increased to 1772 in 2019, from 1606 in 2018. This was predominately driven by SPK listings, and those with type 2 diabetes. Waiting time for SPK decreased by 2 months, to a median of 12 months in 2019, but PTA recipient mean waiting time remained substantially higher, at 24 months, in 2018. Both short- and long-term outcomes, including patient survival, kidney graft survival, and acute rejection-free graft survival, have shown consistent improvement over the last decade. Pancreas graft survival data with the uniform definition of allograft failure is being collected by the Organ Procurement and Transplant Network (OPTN) and will be included in a future report.

OPTN/SRTR 2018 Annual Data Report: Kidney.

Despite the ongoing severe mismatch between organ need and supply, data from 2018 revealed some promising trends. For the fourth year in a row, the number of patients waiting for a kidney transplant in the US declined and numbers of both deceased and living donor kidney transplants increased. These encouraging trends are tempered by ongoing challenges, such as a large proportion of listed patients with dialysis time longer than 5 years. The proportion of candidates aged 65 years or older continued to rise, and the proportion undergoing transplant within 5 years of listing continued to vary dramatically nationwide, from 10% to nearly 80% across donation service areas. Increasing trends in the recovery of organs from hepatitis C positive donors and donors with anoxic brain injury warrant ongoing monitoring, as does the ongoing discard of nearly 20% of recovered organs. While the number of living donor transplants increased, racial disparities persisted in the proportion of living versus deceased donors. Strikingly, the total number of kidney transplant recipients alive with a functioning graft is on track to pass 250,000 in the next 1-2 years. The total number of pediatric kidney transplants remained steady at 756 in 2018. Deeply concerning to the pediatric community is the persistently low level of living donor kidney transplants, representing only 36.2% in 2018.

OPTN/SRTR 2017 Annual Data Report: Kidney.

Many positive trends in kidney transplantation were notable in 2017. Deceased donor kidney transplant rates and counts continued to rise, the kidney transplant waiting list declined for the third year in a row after decades of growth, and both short- and long-term allograft survival continued to improve year over year. In total, more than 220,000 patients were living in the United States with a functioning allograft. With 3 years of data available since implementation of the new kidney allocation system, better prediction of longer-term results of the allocation policy changes became possible. The data also reveal several areas in need of improvement and attention. Overall, the challenge of providing adequate access to kidney transplant persisted nationally, with additional dramatic regional variation. The proportion of living donor kidney transplants in both adults and children continued to fall, and racial disparities in living donor kidney transplant grew in the past decade.

OPTN/SRTR 2016 Annual Data Report: Liver.

Data on adult liver transplants performed in the US in 2016 are no-table for (1) the largest total number of transplants performed (7841); (2) the shortest median waiting time in recent history (11.3 months); (3) continued reduction in waitlist registrations and transplants for hepatitis C-related indications; (4) increasing numbers of patients whose clinical profiles are consistent with non-alcoholic fatty liver disease; and (5) equilibration of transplant rates in patients with and without hepatocellular carcinoma. Despite the increase in the number of available organs, waitlist mortality remained an important concern. Graft survival rates continued to improve. In 2016, 723 new active candidates were added to the pediatric liver transplant waiting list, down from a peak of 826 in 2005. The number of prevalent candidates (on the list on December 31 of the given year) was stable, 408 active and 169 inactive. The number of pediatric living donor liver transplants decreased from a peak of 79 in 2015 to 62 in 2016, with most from donors closely related to the recipients. Graft survival continued to improve over the past decade among recipients of deceased donor and living donor livers.

OPTN/SRTR 2016 Annual Data Report: Kidney.

Data from 2016 show ongoing positive trends in short- and long-term allograft survival, and a decrease in the number of active listed candi- dates for the first time in more than a decade, with a concomitant in- crease in deceased donor kidney transplants. Transplant rates that had changed dramatically for some groups after implementation of the new kidney allocation system in 2014 are stabilizing, allowing for evaluation of new steady states and trends. Many challenges remain in adult kid- ney transplantation, including stagnant rates of living donor transplant, geographic disparities in access to transplant, racial disparities in living donor transplant, and overall a continuing demand for kidneys that far outpaces the supply. For pediatric recipients, a decline in the proportion of living donor transplants is of concern. In 2016, only 34.2% of pediatric transplants were from living donors, compared with 47.2% in 2005. The number of related donors decreased dramatically over the past decade, and the number of unrelated directed transplants performed in pediatric candidates remained low (50).

OPTN/SRTR 2015 Annual Data Report: Liver.

Several notable developments in adult liver transplantation in the US occurred in 2015. The year saw the largest number of liver transplants to date, leading to reductions in median waiting time, in waitlist mortality for all model for end-stage liver disease categories, and in the number of candidates on the waiting list at the end of the year. Numbers of additions to the waiting list and of liver transplants performed in patients with hepatitis C virus infection decreased for the first time in recent years. However, other diagnoses, such as non-alcoholic fatty liver disease and alcoholic cirrhosis, became more prevalent. Despite large numbers of severely ill patients undergoing liver transplant, graft survival rates continued to improve. The number of new active candidates added to the pediatric liver transplant waiting list in 2015 was 689, down from a peak of 826 in 2005. The number of prevalent pediatric candidates (on the list on December 31 of the given year) continued to decline, to 373 active and 195 inactive candidates. The number of pediatric liver transplants peaked at 613 in 2008 and was 580 in 2015. The number of living donor pediatric liver transplants increased to its highest level, 79, in 2015; most were from donors closely related to the recipients. Pediatric graft survival rates continued to improve.

OPTN/SRTR 2015 Annual Data Report: Kidney.

The first full year of data after implementation of the new kidney allocation system reveals an increase in deceased donor kidney transplants among black candidates and those with calculated panel-reactive antibodies 98%-100%, but a decrease among candidates aged 65 years or older. Data from 2015 also demonstrate ongoing positive trends in graft and patient survival for both deceased and living donor kidney transplants, but the challenges of a limited supply of kidneys in the setting of increasing demand remain evident. While the total number of patients on the waiting list decreased for the first time in a decade, this was due to a combination of a decrease in the number of candidates added to the list and an increase in the number of candidates removed from the list due to deteriorating medical condition, as well as an increase in total transplants. Deaths on the waiting list remained flat, but this was likely because of an increasing trend toward removing inactive candidates too sick to undergo transplant.

The Impact of the New Kidney Allocation System on Prior Living Kidney Donors' Access to Deceased Donor Kidney Transplants: An Early Look.

This study investigated the early effects of the new kidney allocation system (KAS) on the access of prior living kidney donors (PLDs) to deceased donor kidney transplants. Using data from the Organ Procurement and Transplantation Network, we compared prevalent and incident cohorts of PLDs in the 1-year periods before and after KAS implementation (pre-KAS group: December 4, 2013, to December 3, 2014, n = 50 [newly listed PLDs]; post-KAS group: December 4, 2014, to December 3, 2015, n = 39). We assessed transplant rates per active patient-year, waiting times, and Kidney Donor Profile Index (KDPI) of transplanted kidneys. Transplant rates were not statistically different before and after KAS implementation for either prevalent (2.37 vs. 2.29, relative risk [RR] 0.96; 95% confidence interval [CI] 0.62-1.49) or incident (4.76 vs. 4.36, RR 0.92; 95% CI 0.53-1.60) candidates. Median waiting time (MWT) to deceased donor kidney transplant for prevalent PLDs in the post-KAS cohort was 102.6 days compared with 82.3 days in the pre-KAS cohort (p = 0.98). The median KDPI for PLD recipients was 31% with KAS versus 23% before KAS (p = 0.02). Despite a sharp decrease in the MWT for highly prioritized candidates with calculated panel reactive antibodies of 98-100% (from >7000 to 1164 days), PLDs still had much shorter waiting times (MWT 102.6 days). The new system continues to provide quick access to high-quality organs for PLDs.

Kidney.

Kidney transplant provides significant survival, cost, and quality-of-life benefits over dialysis in patients with end-stage kidney disease, but the number of kidney transplant candidates on the waiting list continues to grow annually. By the end of 2014, nearly 100,000 adult candidates and 1500 pediatric candidates were waiting for kidney transplant. Not surprisingly, waiting times also continued to increase, along with the number of adult candidates removed from the list due to death or deteriorating medical condition. Death censored graft survival has increased after both living and deceased donor transplants over the past decade in adult recipients. The majority of the trends seen over the past 5 years continued in 2014. However, the new allocation system was implemented in late 2014, providing an opportunity to assess changes in these trends in the coming years.

Liver.

The median waiting time for patients with MELD ≥ 35 decreased from 18 days in 2012 to 9 days in 2014, after implementation of the Share 35 policy in June 2013. Similarly, mortality among candidates listed with MELD ≥ 35 decreased from 366 per 100 waitlist years in 2012 to 315 in 2014. The number of new active candidates added to the pediatric liver transplant waiting list in 2014 was 655, down from a peak of 826 in 2005. The number of prevalent candidates (on the list on December 31 of the given year) continued to decline, 401 active and 173 inactive. The number of deceased donor pediatric liver transplants peaked at 542 in 2008 and was 478 in 2014. The number of living donor liver pediatric transplants was 52 in 2014; most were from donors closely related to the recipients. Graft survival continued to improve among pediatric recipients of deceased donor and living donor livers.

OPTN/SRTR 2013 Annual Data Report: liver.

During 2013, 10,479 adult candidates were added to the liver transplant waiting list, compared with 10,185 in 2012; 5921 liver transplants were performed, and 211 of the transplanted organs were from living donors. As of December 31, 2013, 15,027 candidates were registered on the waiting list, including 12,407 in active status. The most significant change in allocation policy affecting liver waitlist trends in 2013 was the Share 35 policy, whereby organs from an entire region are available to candidates with model for end-stage liver disease scores of 35 or higher. Median waiting time for such candidates decreased dramatically, from 14.0 months in 2012 to 1.4 months in 2013, but the effect on waitlist mortality is unknown. The number of new active pediatric candidates added to the liver transplant waiting list increased to 693 in 2013. Transplant rates were highest for candidates aged younger than 1 year (275.6 per 100 waitlist years) and lowest for candidates aged 11 to 17 years (97.0 per 100 waitlist years). Five-year graft survival was 71.7% for recipients aged younger than 1 year, 74.9% for ages 1 to 5 years, 78.9% ages 6 to 10 years, and 77.4% for ages 11 to 17 years.

OPTN/SRTR 2013 Annual Data Report: kidney.

A new kidney allocation system, expected to be implemented in late 2014, will characterize donors on a percent scale (0%-100%) using the kidney donor profile index (KDPI). The 20% of deceased donor kidneys with the greatest expected posttransplant longevity will be allocated first to the 20% of candidates with the best expected posttransplant survival; kidneys that are not accepted will then be offered to remaining 80% of candidates. Waiting time will start at the time of maintenance dialysis initiation (even if before listing) or at the time of listing with an estimated glomerular filtration rate of 20 mL/min/1.73 m(2) or less. Under the current system, the number of candidates on the waiting list continues to increase, as each year more candidates are added than are removed. Median waiting times for adults increased from 3 years in 2003 to more than 4.5 years in 2009. Donation rates have not increased. Short-term outcomes continue to improve; death-censored graft survival at 90 days posttransplant was 97% or higher for deceased donor transplants and over 99% for living donor transplants. In 2013, 883 pediatric candidates were added to the waiting list; 65.8% of pediatric candidates on the list in 2013 underwent deceased donor transplant. Five-year graft survival was highest for living donor recipients aged younger than 11 years (89%) and lowest for deceased donor recipients aged 11 to 17 years (68%).

OPTN/SRTR 2012 Annual Data Report: kidney.

For most end-stage renal disease patients, successful kidney transplant provides substantially longer survival and better quality of life than dialysis, and preemptive transplant is associated with better outcomes than transplants occurring after dialysis initiation. However, kidney transplant numbers in the us have not changed for a decade. Since 2004, the total number of candidates on the waiting list has increased annually. Median time to transplant for wait-listed adult patients increased from 2.7 years in 1998 to 4.2 years in 2008. The discard rate of deceased donor kidneys has also increased, and the annual number of living donor transplants has decreased. The number of pediatric transplants peaked at 899 in 2005, and has remained steady at approximately 750 over the past 3 years; 40.9% of pediatric candidates undergo transplant within 1 year of wait-listing. Graft survival continues to improve for both adult and pediatric recipients. Kidney transplant is one of the most cost-effective surgical interventions; however, average reimbursement for recipients with primary Medicare coverage from transplant through 1 year posttransplant was comparable to the 1-year cost of care for a dialysis patient. Rates of rehospitalization are high in the first year posttransplant; annual costs after the first year are lower.

OPTN/SRTR 2012 Annual Data Report: liver.

Liver transplant in the us remains a successful life-saving procedure for patients with irreversible liver disease. In 2012, 6256 adult liver transplants were performed, and more than 65,000 people were living with a transplanted liver. The number of adults who registered on the liver transplant waiting list decreased for the first time since 2002; 10,143 candidates were added, compared with 10,359 in 2011. However, the median waiting time for active wait-listed adult candidates increased, as did the number of candidates removed from the list because they were too sick to undergo transplant. The overall deceased donor transplant rate decreased to 42.3 per 100 patient-years, and varied geographically from 18.9 to 228.0 per 100 patient-years. Graft survival continues to improve, especially for donation after circulatory death livers. The number of new active pediatric candidates added to the waiting list also decreased. Almost 75% of pediatric candidates listed in 2009 underwent transplant within 3 years; the 2012 rate of deceased donor transplants among active pediatric wait-listed candidates was 136 per 100 patient-years. Graft survival for deceased donor pediatric transplants was 92.8% at 30 days. Medicare paid for some or all of the care for more than 30% of liver transplants in 2010.

OPTN/SRTR 2012 Annual Data Report: pancreas.

The number of pancreas transplants has decreased over the past decade, most notably numbers of pancreas after kidney (pak) and pancreas transplant alone (pta) procedures. This decrease may be mitigated in the future when changes to national pancreas allocation policy approved by the Organ Procurement and Transplantation Network Board of Directors in 2010 are implemented. The new policy will combine waiting lists for pak, pta, and simultaneous pancreas-kidney (spk) transplants), and give equal priority to candidates for all three procedures. This policy change may also eliminate geographic variation in waiting times caused by geographic differences in allocation policy. Deceased donor pancreas donation rates have been declining since 2005, and the donation rate remains low. The outcomes of pancreas grafts are difficult to describe due to lack of a uniform definition of graft failure in the transplant community. However long-term survival is better for spk versus pak and pta transplants. This may represent the difficulty of detecting rejection in the absence of a simultaneously transplanted kidney. The challenges of pancreas transplant are reflected in high rates of rehospitalization, most occurring within the first 6 months posttransplant. Pancreas transplant is associated with higher incidence of rejection compared with kidney transplant.

Optimizing the program-specific reporting of pancreas transplant outcomes.

The Scientific Registry of Transplant Recipients is charged with providing program-specific reports for organ transplant programs in the United States. Monitoring graft survival for pancreas transplant programs has been problematic as there are three different pancreas transplant procedures that may have different outcomes, and analyzing them separately reduces events and statistical power. We combined two consecutive 2.5-year cohorts of transplant recipients to develop Cox proportional hazards models predicting outcomes, and tested these models in the second 2.5-year cohort. We used separate models for 1- and 3-year graft and patient survival for each transplant type: simultaneous pancreas-kidney (SPK), pancreas after kidney (PAK) and pancreas transplant alone (PTA). We first built a predictive model for each pancreas transplant type, and then pooled the transplant types within centers to compare total observed events with total predicted events. Models for 1-year pancreas graft and patient survival yielded C statistics of 0.65 (95% confidence interval, 0.63-0.68) and 0.66 (0.61-0.72), respectively, comparable to C statistics for 1-year patient and graft survival for other organ transplants. Model calibration (Hosmer-Lemeshow method) was also acceptable. We conclude that pooling the results of SPK, PAK and PTA can produce potentially useful models for reporting program-specific pancreas transplant outcomes.

OPTN/SRTR 2011 Annual Data Report: pancreas.

Numbers of pancreas transplants have been decreasing over the past decade, but outcomes continue to improve for all types: simultaneous pancreas-kidney transplant, pancreas after kidney transplant (PAK), and pancreas transplant alone (PTA). The most notable decrease occurred for PAK transplants, possibly due in part to decreases in numbers of living donor kidney transplants. The number of new candidates on the pancreas transplant waiting list has decreased steadily since 2000; only 1005 active candidates were added in 2011. Transplant rates for all pancreas transplant types reached a low in 2011 of 34.9 transplants per 100 wait-list years. Deceased donation rates have also been decreasing since 2005, but use of donation after circulatory death has been gradually increasing. The discard rate in 2011 was 27.7%, and higher for pancreata recovered from older donors. Improved outcomes during the early posttransplant period largely reflect improved donor and recipient selection and improved technical strategies. Inconsistent definitions of graft failure across reporting centers creates an ongoing challenge in the interpretation of outcome data for pancreas transplants. Rates of posttransplant re-hospitalization are high, most occurring in the first 6 months. Rejection rates are highest for PTA recipients, who also experience higher incidence of posttransplant lymphoproliferative disorder.

Analysis of Pressure Variations in a Low-Pressure Nickel-Hydrogen Battery- Part 2: Cells with Metal Hydride Storage.

A sub-atmospheric pressure nickel hydrogen (Ni-H(2)) battery with metal hydride for hydrogen storage is developed for implantable neuroprosthetic devices. Pressure variations during charge and discharge of the cell are analyzed at different states of charge and are found to follow the desorption curve of the pressure composition isotherm (PCI) of the metal hydride. The measured pressure agreed well with the calculated theoretical pressure based on the PCI and is used to predict the state of charge of the battery. Hydrogen equilibration with the metal hydride during charge/discharge cycling is fast when the pressure is in the range from 8 to 13 psia and slower in the range from 6 to 8 psia. The time constant for the slower hydrogen equilibration, 1.37h, is similar to the time constant for oxygen recombination and therefore pressure changes due to different mechanisms are difficult to estimate. The self-discharge rate of the cell with metal hydride is two times lower in comparison to the cell with gaseous hydrogen storage alone and is a result of the lower pressure in the cell when the metal hydride is used.