Pancreas Allocation for Whole Organ and Islet Transplantation
Pancreas Allocation for Whole Organ and Islet Transplantation
In order to develop a national allocation scheme for donor pancreases, factors affecting waiting time and transplant outcomes in the United States (US) and United Kingdom (UK) were analyzed and compared. Blood group, sensitization, dialysis requirement, and whether the patient was waiting for a kidney and pancreas or pancreas alone affected waiting time in both countries; ethnicity and body mass index (BMI) also affected waiting time in the US. Ninety-day pancreas survival was similar in the UK and US, and was poorer for patients receiving a pancreas alone, with older donors, higher BMI and longer duration of ischemia in both countries. Factors affecting outcome, together with published data on factors affecting islet transplantation, informed the development of a points based allocation scheme for deceased donor pancreases in the UK providing equitable access for both whole organ and islet recipients through a single waiting list. Analysis of the allocation scheme 3 years after its introduction in December 2010 showed that the results were broadly as simulated, with a significant reduction in the number of long waiting patients and an increase in the number of islet transplants. There remains a surplus of highly sensitized patients in the waiting list, which the scheme should address in time.
Pancreas transplantation is an established treatment for patients with life-threatening complications of diabetes, but access to such transplants is variable. In the United Kingdom (UK), even though the first pancreas transplant was performed in 1979, the widespread adoption of pancreas transplantation had been slow, with only 32 pancreas transplants performed in 2000. In contrast, an estimate based on the proportion of young diabetic patients listed for kidney transplantation suggested 200 patients a year might benefit.
In 2002, a task force was established to develop pancreas transplantation in the UK. This task force comprised representatives from the seven transplant centers performing pancreas transplants at the time. The group included representation from commissioners and UK Transplant (later renamed the Organ Donation and Transplantation [ODT] Directorate of National Health Service Blood and Transplant [NHSBT]). National Commissioning of Pancreas Transplantation was implemented in Scotland in 2000, and followed in England in 2004 and in Wales in 2006. The National Health Service (NHS) covers all the costs of the transplant and postoperative care, including immunosuppression, for the life of the patient.
At that time, the task force devised a basic allocation scheme, which divided the UK into seven equal zones each centerd around a single transplant center; each center had the first choice of all deceased donor pancreases that were offered within their donation zone. Allocation of pancreases to patients on an individual center's waiting list was left to that center's discretion, with the stipulation that recipients should have an identical blood group to the donor. It was assumed that referrals for transplantation would follow a similar zonal pattern to donor organ allocation, but this did not happen with the result that, although each center had roughly a seventh of the national pancreas donors, some had much more than a seventh of the national waiting list; zones were therefore reviewed regularly and adjusted to accommodate these differences. The zones were further readjusted to accommodate addition of the Welsh pancreas transplant program.
This zonal allocation scheme had several shortcomings. In spite of adjusting the zones, there remained a marked inequality of waiting times to transplantation between centers. The scheme resulted in each center having access to a limited pool of donors that was insufficient to address the increasing numbers of patients on the waiting list who were sensitized to human leucocyte antigens (HLA). Lastly there was no transparency and considerable variability in how pancreases were allocated within each center.
To complicate allocation further, pancreatic islet transplantation had been nationally commissioned in England in 2008 and Scotland in 2009, but the three isolation laboratories were only accessing to pancreases that had been deemed unusable for whole organ transplantation, often with long ischemic times, and as a consequence they struggled to obtain satisfactory islet yields. The inequity of access to donor pancreases for both whole organ and islet transplantation prompted the development of a national patient-specific allocation scheme.
A second task force was convened to examine available data and develop a scheme for the fair allocation of donor pancreases for both whole organ and islet transplantation; one that would afford potential recipients an equal opportunity of getting a pancreas and reduce variability between centers. As a prelude to this, the criteria for suitability for both islet and whole pancreas transplant waiting lists were reviewed. These criteria are regularly evaluated and updated, and are available on http://odt.nhs.uk/transplantation/guidance-policies/. Briefly, patients with insulin-dependent diabetes and renal failure (glomerular filtration rate less than 20 mls/min) are eligible for combined pancreas and kidney transplantation. Patients with life-threatening hypoglycemic unawareness are eligible for solitary pancreas or islet transplantation. Patients with a functioning kidney transplant and poor glucose control are also eligible for a pancreas or islet after kidney. Patients with type 2 diabetes must have a body mass index (BMI) less than 30 kg/m. An appeals panel was established to discuss listing of patients who fell outside of these criteria.
The task force reviewed UK data on whole organ transplantation looking at factors associated with waiting time and outcomes following transplantation. Since the UK dataset was relatively small, data were also obtained from the Organ Procurement and Transplant Network (OPTN). The OPTN data were first compared to UK data to establish whether similar factors accounted for both the time waiting for a transplant and the outcomes following transplantation. Those factors identified in both United States (US) and UK datasets were then used to establish a national organ-sharing algorithm. There were insufficient data to use the same process for islet transplantation, so assumptions were made based on published data where available.
This paper describes the analysis that underpinned the final UK pancreas allocation scheme, which was introduced in December 2010, and the results of that scheme over the first 3 years. Importantly, for the first time, organ allocation for both islet and whole organ recipients has been managed by means of a single waiting list.
Abstract and Introduction
Abstract
In order to develop a national allocation scheme for donor pancreases, factors affecting waiting time and transplant outcomes in the United States (US) and United Kingdom (UK) were analyzed and compared. Blood group, sensitization, dialysis requirement, and whether the patient was waiting for a kidney and pancreas or pancreas alone affected waiting time in both countries; ethnicity and body mass index (BMI) also affected waiting time in the US. Ninety-day pancreas survival was similar in the UK and US, and was poorer for patients receiving a pancreas alone, with older donors, higher BMI and longer duration of ischemia in both countries. Factors affecting outcome, together with published data on factors affecting islet transplantation, informed the development of a points based allocation scheme for deceased donor pancreases in the UK providing equitable access for both whole organ and islet recipients through a single waiting list. Analysis of the allocation scheme 3 years after its introduction in December 2010 showed that the results were broadly as simulated, with a significant reduction in the number of long waiting patients and an increase in the number of islet transplants. There remains a surplus of highly sensitized patients in the waiting list, which the scheme should address in time.
Introduction
Pancreas transplantation is an established treatment for patients with life-threatening complications of diabetes, but access to such transplants is variable. In the United Kingdom (UK), even though the first pancreas transplant was performed in 1979, the widespread adoption of pancreas transplantation had been slow, with only 32 pancreas transplants performed in 2000. In contrast, an estimate based on the proportion of young diabetic patients listed for kidney transplantation suggested 200 patients a year might benefit.
In 2002, a task force was established to develop pancreas transplantation in the UK. This task force comprised representatives from the seven transplant centers performing pancreas transplants at the time. The group included representation from commissioners and UK Transplant (later renamed the Organ Donation and Transplantation [ODT] Directorate of National Health Service Blood and Transplant [NHSBT]). National Commissioning of Pancreas Transplantation was implemented in Scotland in 2000, and followed in England in 2004 and in Wales in 2006. The National Health Service (NHS) covers all the costs of the transplant and postoperative care, including immunosuppression, for the life of the patient.
At that time, the task force devised a basic allocation scheme, which divided the UK into seven equal zones each centerd around a single transplant center; each center had the first choice of all deceased donor pancreases that were offered within their donation zone. Allocation of pancreases to patients on an individual center's waiting list was left to that center's discretion, with the stipulation that recipients should have an identical blood group to the donor. It was assumed that referrals for transplantation would follow a similar zonal pattern to donor organ allocation, but this did not happen with the result that, although each center had roughly a seventh of the national pancreas donors, some had much more than a seventh of the national waiting list; zones were therefore reviewed regularly and adjusted to accommodate these differences. The zones were further readjusted to accommodate addition of the Welsh pancreas transplant program.
This zonal allocation scheme had several shortcomings. In spite of adjusting the zones, there remained a marked inequality of waiting times to transplantation between centers. The scheme resulted in each center having access to a limited pool of donors that was insufficient to address the increasing numbers of patients on the waiting list who were sensitized to human leucocyte antigens (HLA). Lastly there was no transparency and considerable variability in how pancreases were allocated within each center.
To complicate allocation further, pancreatic islet transplantation had been nationally commissioned in England in 2008 and Scotland in 2009, but the three isolation laboratories were only accessing to pancreases that had been deemed unusable for whole organ transplantation, often with long ischemic times, and as a consequence they struggled to obtain satisfactory islet yields. The inequity of access to donor pancreases for both whole organ and islet transplantation prompted the development of a national patient-specific allocation scheme.
A second task force was convened to examine available data and develop a scheme for the fair allocation of donor pancreases for both whole organ and islet transplantation; one that would afford potential recipients an equal opportunity of getting a pancreas and reduce variability between centers. As a prelude to this, the criteria for suitability for both islet and whole pancreas transplant waiting lists were reviewed. These criteria are regularly evaluated and updated, and are available on http://odt.nhs.uk/transplantation/guidance-policies/. Briefly, patients with insulin-dependent diabetes and renal failure (glomerular filtration rate less than 20 mls/min) are eligible for combined pancreas and kidney transplantation. Patients with life-threatening hypoglycemic unawareness are eligible for solitary pancreas or islet transplantation. Patients with a functioning kidney transplant and poor glucose control are also eligible for a pancreas or islet after kidney. Patients with type 2 diabetes must have a body mass index (BMI) less than 30 kg/m. An appeals panel was established to discuss listing of patients who fell outside of these criteria.
The task force reviewed UK data on whole organ transplantation looking at factors associated with waiting time and outcomes following transplantation. Since the UK dataset was relatively small, data were also obtained from the Organ Procurement and Transplant Network (OPTN). The OPTN data were first compared to UK data to establish whether similar factors accounted for both the time waiting for a transplant and the outcomes following transplantation. Those factors identified in both United States (US) and UK datasets were then used to establish a national organ-sharing algorithm. There were insufficient data to use the same process for islet transplantation, so assumptions were made based on published data where available.
This paper describes the analysis that underpinned the final UK pancreas allocation scheme, which was introduced in December 2010, and the results of that scheme over the first 3 years. Importantly, for the first time, organ allocation for both islet and whole organ recipients has been managed by means of a single waiting list.
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