UNOS DonateLife

January 15, 1996

UNOS Rationale for Objectives of Equitable Organ Allocation

This article contains data current to its publication in 1994, but it is still useful in stating the goals and objectives of the UNOS allocation system.

The goal of the UNOS organ allocation system is to achieve the following objectives in balance with one another. The policy must take into consideration all of the objectives rather than focus on one objective and not the others. Therefore, the policy must strike a balance among competing, and often conflicting, objectives.

• Maximize the availability of transplantable organs by:
  
  • Promoting consent to donate;
  • Enhancing procurement efficiency;
  • Minimizing organ discards; and
  • Promoting efficiency in organ distribution and allocation.
  
  Organ donation, procurement, distribution and allocation are all intrinsically linked together. Thus, organ allocation cannot be addressed in a vacuum without considering the impact of any allocation policy on the supply of transplantable organs. The policy should strive to avoid loss of organs, and it should also promote recovery of the most organs possible. The policy must engender confidence in the general public that the policy is fundamentally fair to accomplish these two purposes. It must promote efficient organ recovery at the same time. Organs have severely limited timeframes in which they remain useable for transplants. Therefore, the policy must also promote efficient organ distribution to avoid organs becoming less beneficial or wasted because they were not transplanted soon enough.
• Maximize patient and graft survival.
  
  The way in which donor organs are matched with waiting recipients may affect the survival of the transplant itself (graft survival) and the survival of the patient. Many medical factors determine whether a transplant is medically feasible at all and whether the chances of long-term success are as high as possible. The allocation policy should not result in an organ being offered to a transplant center for a particular patient if the transplant is not medically feasible (e.g., positive crossmatch, inappropriate organ size or incompatible blood type).
  
  The degree of medical compatibility between the donor and candidate may also affect the long-term survival. For example, it is widely accepted that transplanting a kidney with tissue antigens that perfectly match those of the recipient stands a better chance of long-term success than transplanting a kidney from a donor whose antigens do not match. Two years after a transplant, 86% of patients who receive a perfect "6 antigen match" have a functioning kidney. In contrast, only 72% of patients who receive a poorly matched kidney have a functioning graft two years after transplant.
  
  The Waiting List patient's medical condition may also influence whether the transplant will be successful. For example, 51% of patients who receive a liver transplant when they are gravely ill (hospitalized in the intensive care unit just prior to transplant) survive at least two years. In contrast, 77-80% of liver Waiting List patients who receive transplants before they are sick enough to be continuously hospitalized survive at least two years. Slightly more than 10% of patients who receive a liver transplant when they are in the most urgent status are retransplanted as compared to 6 to 8% in the less urgent categories.
  
  Liver Patient Survival, by Patient Description at Time of Transplant
  Patients Transplanted Between October 1, 1987 and December 31, 1991
  
  Heart Patient Survival, By Patient Description at Time of Transplant
  Patients Transplanted Between October 1, 1987 and December 31, 1991
  
  It is important for all transplant candidates as a group that the allocation policy try to achieve the best transplant survival rates possible. This reduces the number of organs needed for patients whose grafts fail. Every repeat transplant denies someone else either a life-saving opportunity or a chance at a better quality of life because there are not enough organs available for everyone who needs a transplant. A policy that results in low overall survival by transplanting patients whose condition has worsened to the point that their chances of survival have diminished will perpetuate the likelihood that patients who are not as sick and have a higher probability of a successful transplant will be forced to wait until their condition worsens and their chances for success are also diminished.
• Minimize disparities in consistently measured waiting times until an offer of an organ for transplantation is made among patients with similar or comparable medical/demographic characteristics. (At the present time, there are no Waiting List criteria; therefore, commencement of waiting time varies among patients.)
  
  The policy should be designed to treat people in similar situations as much the same as possible, in order to promote overall equity. It is unreasonable to expect that every patient will have the same opportunity to receive a transplant, because circumstances are different for individual patients and for certain groups of patients with special conditions. For example, patients with panel reactive antibody (PRA) levels of 99 (meaning that the patient's immune system will reject kidneys from approximately 99% of all donors) will not have the same opportunities to receive kidney transplants as patients with PRAs of zero.
  
  Allocation policy can do little to equalize opportunities for kidney transplants between these two patient groups. However, policy must do as much as possible to see that patients with high PRA levels receive opportunities for transplants, even if it cannot guarantee equal results (i.e., waiting time until a transplant) for all patients regardless of circumstances.
  
  Currently, "waiting time" accumulation begins when a patient is placed on the UNOS Waiting List by a physician. At present, there are no rules governing what the patient's condition must be in order to be added to the list. Such a decision is left to each physician's judgement. Therefore, differences in medical practice may result in different waiting times for different patients. Policy must try to reduce waiting time differences for patients, taking varying medical practices into account so that waiting times are measured similarly for everyone.
  
  In the U.S. medical system, patients have much input into their medical care. Waiting List patients have the ability to accept or reject the opportunity for transplantation whenever it arises. Similarly, the physician may exercise judgement in determining whether a specific organ, once available for transplant, is suitable for the patient. Therefore, an allocation policy can only be judged in terms of the opportunities it provides for patients to receive transplants.
• Minimize deaths while waiting for a transplant.
  
  In 1992, approximately 2,600 people died while waiting for transplants. The policy should provide a degree of priority to patients who need transplants most urgently to minimize the number of Waiting List deaths. Critically ill patients are the ones most likely to die waiting for a transplant as the following table illustrates. The table shows the percentage of Liver Waiting List deaths according to medical urgency status for a three-year period. It does not show the percentage of Liver Waiting List patients who died. The most critically ill liver patients in this table, are those known as Status 4 patients. Their need for liver transplants is the most urgent. Current liver allocation policy gives highest priority to local Status 4 patients. If the policy did not give priority to Status 4 patients, the number and percentage of Waiting List deaths in that category would be even higher. However, because patients in the other status categories also die while waiting (60% of all deaths reported are for patients who are not Status 4), livers are currently offered for local patients in other medical urgency categories (Status codes 1, 2 and 3) before they are offered to Status 4 patients outside the local area but within the same region as the donor. If there is no suitable patient in the region, the liver is then offered nationwide, first for Status 4 patients, then for others.
  
  The Percentage of Liver Waiting List Deaths Each Year,
  According to Medical Urgency Status at Time of Death

  Status 1 - end stage disease, but at home and functioning normally
  Status 2 - requires continuous medical care but not continuous hospitalization
  Status 3 - continuously hospitalized but not in the intensive care unit
  Status 4 - in the intensive care unit, with a life expectancy of less than 7 days unless transplanted

  UNOS organ allocation policy is intended to minimize the number of deaths while waiting for a transplant, within the framework of the other objectives that also must be met.
• Maximize opportunity for patients with biological or medical disadvantages to receive a transplant. 
  
  Allocation policy should make it possible for patients with certain medical or biological disadvantages to receive optimal opportunities for transplants. Some patients have biological or medical conditions that make it more difficult for them to receive a transplant. The allocation policy must sometimes give these patients additional consideration in order for them to receive an equitable opportunity. For example, it is very difficult to find compatible kidneys for patients with high levels of antibodies against foreign tissue antigens known as human leukocyte antigens (HLA). Such patients are said to be highly sensitized. Patients can develop antibodies to HLA after blood transfusions, pregnancies, or previous transplants. Highly sensitized patients would rarely be offered a suitable kidney if the policy did not give them extra consideration. In the current system, patients with high levels of certain antibodies receive extra priority (4 extra kidney allocation points) because it is difficult to find suitable kidneys for them. As a result, they get more opportunities to receive transplants than they would without extra points. Some argue that patients who have a high PRA because of a previous transplant should not be given priority over patients who have not yet received their first transplant. Current policy makes no distinction between persons needing first or repeat transplants.
  
  Children are medically disadvantaged, because they do not grow and develop well without normal kidney function. The longer they wait for kidneys, the more their growth is permanently stunted. Therefore, it seems fair to give children extra consideration in the kidney allocation policy.
  
  Another example of biological disadvantage involves patients with blood type O. Waiting List patients with blood type O can receive organs only from donors with type O. In contrast, organs from donors with blood type O can be transplanted into patients of any blood type. As a result, blood type O organs would mostly be given to patients of other blood types and fewer would be available for blood type O patients who make up a very large part of the Waiting List. The current kidney allocation policy helps keep kidneys available for type O patients by requiring most type O kidneys to go only to type O Waiting List patients. The purpose of this policy is to make the system more equitable for type O patients who, by no fault of their own, are disadvantaged by their blood type.
  
  A person's race per se is not a factor in the present allocation system. However, it has become clear in the U.S., where the organ donor and organ recipient populations are predominantly white, that Waiting List patients of other races have significantly longer average waiting times before being transplanted than do whites. There may be many confounding variables affecting these differences. Several biological factors are known to contribute to the problem. For example, certain blood types (types O and B) are more common among blacks than among whites. Blacks represent 12% of the general population and donate 12% of the kidneys that are transplanted. However, 32% of patients awaiting a kidney transplant are black because there is a higher incidence of end stage renal disease among blacks. It is more difficult to provide kidney transplants for black patients with type O or B blood because more than 80% of kidney donors are white and 12% are black. Another serious problem for many black renal patients is that of antigen sensitization. Many black renal Waiting List patients are highly sensitized, and it is very difficult to find a compatible kidney for a highly sensitized patient, whether the patient is black or white. The problem has a tendency to perpetuate itself because long waiting times necessitate more transfusions (for kidney patients), which in turn increase antigen sensitization. Once transplanted, sensitized patients lose their grafts more often, leading to increased sensitization, long waiting times for repeat transplants, and more transfusions.
• Minimize effects related to geography.
  
  Ideally, allocation policy should not disadvantage certain patients because of the part of the country in which they live. However, the availability of deceased donor organs can vary widely from one area to another for many reasons. It is not currently feasible to distribute organs using a single national Waiting List because they can last only a limited time without oxygenated blood and for other technical reasons (e.g., the necessity of crossmatching before kidney transplants). Doing so might distribute organs more equally across the nation, but it would result in unacceptable organ damage and wasted organs. For this reason, organs are currently distributed to patient populations that are smaller than the entire national population but are not so large that transporting organs from donor to patient will result in unacceptable ischemia time (time without oxygenated blood).
  
  It is difficult to define the ideal size of a geographic organ distribution area, partially because the amount of acceptable ischemia time differs for each organ type. Differences across the country in population density (which affects both donor availability and Waiting List length), productivity levels of OPOs, and transplant center practices complicate the problem. An important consideration in kidney distribution is whether preliminary crossmatching can be done before shipping a kidney. Crossmatching can predict immediate kidney rejection and helps prevent organ wastage. However, this process requires time and access to recently drawn Waiting List patient blood serum. Therefore, the ability to do preliminary crossmatching is diminished, the larger the geographic area for distribution.
  
  The current system attempts to reduce geographical differences in organ distribution. The OPTN keeps records on every patient in the U.S. waiting for a deceased donor organ transplant. As each organ becomes available, it is generally allocated first using a list of patients known as the local list. That list includes patients who are registered for transplants at specific transplant centers within the OPO service area where the donor is located. If the organ is not suitable for a patient on the local list, a larger list is used, which for organs other than hearts and lungs, includes all patients listed in the same UNOS geographic region as the donor. For hearts, concentric circles of 500 mile radii from the site of the donor are used. The national list is used for organs other than hearts and lungs only if there is no suitable local or regional patient. An exception to this process exists in the kidney allocation system, according to which, each kidney is compared first with the composite national list, in an effort to identify all patients whose HLA identically match those of the donor.
  
  The policy must be monitored and reassessed continually. Factors such as acceptable ischemic times may change with advances in organ preservation permitting larger initial allocation areas for certain types of organs. It may be beneficial to uncouple organ allocation from the individual service areas of OPOs despite historical and legal precedent for not doing so (see Appendix A-Current Assumptions and Constraints).
• Allow convenient access to transplantation.
  
  Allowing convenient access to transplantation for patients relates to the principle of striving to give equal consideration to medical utility and justice. A primary concern to many patients who require transplantation is that they be able to receive medical treatment without the burden of traveling great distances. The seriousness of their illness for some patients will also affect their ability to travel great distances in order to receive a transplanted organ. Local hospitalization may also be important so that transplant recipients can receive visits from close family members and maintain their morale during recovery. Therefore, geographic and logistical concerns should be considered in the organ allocation system so that patients who cannot medically, physically, or financially afford to travel great distances to receive a transplant are not disadvantaged or denied access to transplantation. Some argue that permitting patients to be on multiple local lists is inequitable because it creates a disadvantage for patients who are not able to travel to multiple transplant centers. The same argument has been made against a policy that would result in most organs going to a few large transplant centers, because such a policy could unfairly favor patients wealthy enough to travel to those centers and would disadvantage poor patients unable to travel. Current policy does not interfere with a patient's freedom to take whatever steps felt appropriate to seek medical treatment.
  
  The number of transplant programs in the country at which patients may have access to transplants is not currently limited by UNOS. However, there may be a correlation between the number of transplants performed and a transplant center's survival rates (taking patient mix and any other appropriate factors into account). If it is found that transplant centers that perform very few transplants do not have acceptable survival rates, the allocation policy may take such information into account. UNOS has minimum criteria that transplant programs must meet to be approved, but the criteria do not limit the number of programs that are approved to provide each kind of transplant procedure. The criteria do require that surgeons and physicians have sufficient training and experience to provide quality patient care and that the transplant center's physical facilities, equipment, and support services also be sufficient. UNOS has no legal authority to limit the number of transplant programs. UNOS Bylaws do, however, provide that transplant programs whose patient or graft survival rates fall below the expected rate by more than a statistically derived threshold (based upon national averages considering patient mix) are subject to evaluation and probation if the difference cannot be adequately explained by patient mix or some other unique clinical aspect.
• Minimize overall transplantation-related costs.
  
  Organ transplantation is an ever-changing field of medicine that involves complex, sophisticated and rapidly advancing technologies and procedures. Transplants often save lives. At a minimum, they improve the patient's quality of life and that of the patient's family. The benefits of transplantation, are huge, but costly. While no one can put a price on the value of a new chance at human life, the supply of funds available to cover transplantation costs is limited. A primary objective of the national allocation policy is to maximize the benefits of transplantation to patients while minimizing all transplantation-related costs. This objective is affected by the following factors:
  
  
  • Costs of Transporting Organs. When a donated organ is allocated to a patient whose hospital is different from the facility that recovers the organ, this organ must first be transported to the patient's hospital before it can be transplanted. Use of the organ within shorter, rather than longer, distances from the donor facility may be less expensive due to lower organ transportation costs and less complicated travel arrangements. Because hearts, lungs, pancreases, and, to a lesser extent, livers cannot remain viable for long without an oxygenated blood supply, transportation of these organs over long distances usually requires air transport, at great cost. When commercial flights are not available within organ preservation limits, chartered aircraft are required, further increasing the transportation costs. Perhaps more significantly, hearts and lungs with long ischemic times generally do not work as well as those with shorter ones. As a result, a patient's intensive care unit and overall hospital stay may be prolonged, thus increasing costs substantially, and the benefit derived from the transplant may be decreased. The correlation between ischemic time and organ quality should be continually reevaluated for all organs.
  • Costs of Transporting Patients. Patients do not always live in the geographic area where their chosen transplant center is located. Greater numbers of transplant centers dispersed across the United States provide more opportunity for patients to select transplant centers that are close to them, allowing lower costs for patient and organ transportation. 
  • Alternate Forms of Available Medical Treatment. Unlike patients whose lives depend on receiving a transplant, patients with end stage renal disease often can be treated either by dialysis or by renal transplantation. According to HCFA, the government's cost of dialysis averages $40,000 annually and its cost for a kidney transplant averages $87,000 for the procedure itself together with all related costs during the first year. Costs during each year thereafter total about $12,000. Therefore, during the third year after transplant, a successful kidney transplant normally becomes more cost effective than dialysis and when one considers the overall cost of transplantation, including unsuccessful transplants, the expected payback period is approximately 41/2 years. 
  • Patient Medical Urgency at Time of Transplant. Transplantation costs increase with each day a patient is cared for in the hospital either before or after transplant. Costs are especially high if the patient requires care in a monitored or intensive care unit. Transplanting the sickest patients first means transplanting many patients who require prolonged hospitalization both prior to the transplant as well as during recovery, because of their poor condition before the transplant. Also, due to their poor medical condition before the transplant, patients who receive their transplant when they are very sick lose their graft more often than patients who receive transplants before they become critically ill. For example, two years after a liver transplant, 75% of patients who received their transplants while they were still relatively healthy still had functioning grafts. In contrast, only about 50% of patients who were in intensive care immediately before transplant still had functioning grafts two years later. When grafts fail, patients require additional hospitalization, with, again, a lower chance of survival. When patients receive transplants before their medical condition badly deteriorates, the chances of graft failure are greatly reduced and hospital stays (and costs) before and after transplant are less.
  • Provide for flexibility in policy making.
    
    Transplantation is a rapidly changing field. New innovations and discoveries are published on a regular basis. New data are collected and analyzed continuously. Therefore, an essential feature of the organ allocation policy is flexibility.
  • Provide for accountability and public trust.
    
    The implementation and operation of the organ allocation policy must be accomplished in a way that provides for accountability by all  participants so as to engender trust among patients, transplant professionals and the public. The policy must be simple and practical enough to permit thorough monitoring designed both to ensure compliance and to evaluate the policy's impact. Therefore, uniform, timely and  accurate records must be kept by transplant centers, OPOs and histocompatibility labs and be made available to UNOS to enable UNOS to perform audits, analyze data, and assess the operation and outcome of allocation policy.