This glossary provides descriptions of some of the terms used in the Annual Report. For additional details, please see the Technical Notes.

ABO Blood Type
Includes blood types O, A, B, and AB.

ACOT
Advisory Committee on Organ Transplantation.

Advisory Committee on Organ Transplantation (ACOT)
Formed under the U.S. Department of Health and Human Services (HHS) in autumn of 2000, the ACOT was convened in order to strengthen the scientific, medical, and public involvement in HHS oversight of transplantation policy. In particular, ACOT provides independent review and advice to HHS concerning revised organ allocation policies being developed by the nation's transplantation network.

Allocation Policies
Rules or policies, generally based upon medical criteria, established by the OPTN to guide and regulate organ allocation or distribution in the United States.

Annual Death Rate
Specifically referenced in this publication as the "annual death rate per 1,000 patient years at risk," it is the number of deaths for every 1,000 patient years on the waiting list. The rate is calculated by dividing the number of patients who died in a given year by the sum of the years (including partial years) that patients spent waiting and then multiplying by 1,000. The number 1,000 was chosen, rather than the more familiar 100, because death rates in some categories may be so low that they produce a small percentage.

Antibody
A protein made by the body's immune system in response to a foreign substance. Exposure to foreign cells from a previous transplant, blood transfusion, or pregnancy may cause a transplant recipient to make antibodies that can react against subsequently transplanted cells, tissues, or organs.

Antigen
A foreign molecule or substance with the capacity to trigger an immune response. Special antigens on the surface of each cell indicate to the immune system whether or not that cell is foreign or native to an individual.

AOPO
Association of Organ Procurement Organizations.

Cadaveric Donor
An individual whose tissues or organs are donated after his or her death. Cadaveric donations are from two sources: patients who have suffered brain death and patients whose hearts have irreversibly stopped beating. The later group is referred to as "non-heartbeating donors."

Cadaveric Transplant
The transplant of an organ from a cadaveric donor.

Censored
Used with survival, median waiting time before transplant, and time to transplant analyses. Censoring allows the analysis to use all of the follow-up data for a case even if the follow-up period is incomplete. For instance, in the survival analyses, a patient is censored when he is reported as "lost to follow-up."

Centers for Medicare and Medicaid Services (CMS)
CMS (formerly the Health Care Financing Agency or HCFA) is an agency of the United States Department of Health and Human Services. CMS administers the Medicare and Medicaid programs, which provide health care to America's aged and indigent populations (about one in every four Americans, including nearly 18 million children), and nursing home coverage for low-income elderly people.

Chimerism
The simultaneous existence and function of components of both the donor's and the recipient's immune systems in the same patient resulting in cross-regulation of immune system activities.

CMS
Centers for Medicare and Medicaid Services.

Cohort
The observations selected for a study based on a specific time period. For example, in this report the cohort of transplant recipients includes all transplants performed between 1991 and 2000.

Cold Ischemia Time
The time interval that begins when an organ is cooled with a cold perfusion solution after organ procurement surgery and ends when the organ is re-perfused at implantation.

Compliance
Adherence to protocols or standards. In the context of this report, "compliance" refers to the adherence of OPTN members to the policies and bylaws of the OPTN. Appendix G contains more information on compliance and the role of the OPTN in enforcing compliance.

Confidence Limits
Used with median time to transplant and median waiting time before transplant analyses, confidence limits represent a range of days in which we expect the median to fall. For example, the median waiting time in 2000 for heart registrants age 11-17 was 105 days; the 95% confidence limits for this group were 62 (lower limit) and 195 (upper limit). This means that we can be 95% confident that half of the heart registrants age 11-17 were transplanted in the first 62 to 195 days after registration. Confidence limits show how variable waiting times were for different groups of patients. A narrow range between the lower and upper limit means there is less variability in waiting time, while a broad range indicates greater variability. This can be helpful to patients in that it gives them a better idea of the range of waiting time to expect.

Crossmatch
A test to detect preformed antibodies in a potential recipient's blood against antigens on the surface of a potential donor's cells. A positive crossmatch means that the recipient has antibodies against the donor's cells. With few exceptions, a positive crossmatch makes successful transplantation between that donor and recipient pair impossible.

Death Rate
The death rate is calculated as the number of patient deaths per 1,000 patient years on the waiting list. The rate is calculated based on the amount of time patients are waiting. Therefore, the smaller the death rate, the fewer the number of deaths per 1,000 patient years waiting.

Division of Transplantation (DoT)
The DoT is a component of the Office of Special Programs in the Health Resources and Services Administration (HRSA). The DoT regulates and provides federal oversight and funding support for the nation's organ procurement, allocation, and transplantation system; coordinates national organ and tissue donation activities; funds research to improve donation rates; and administers the National Bone Marrow Registry program.

Donor
An individual who supplies living tissue to be used in another person, as a person (cadaveric or living) who furnishes an organ for transplantation.

DoT
Division of Transplantation.

End-Stage Organ Failure
The irreversible and permanent need for organ replacement therapy. For kidney, liver, heart, lung, pancreas, and intestine, there is the option of transplantation.

End-Stage Renal Disease (ESRD)
The irreversible and permanent kidney failure that requires either dialysis or transplant as renal replacement therapy.

Ethnicity
For purposes of this report, race and Hispanic/Latino ethnicity are defined separately, as reported on the data collection forms. Race and ethnicity are not considered mutually exclusive.

Expanded Donor
A donor that is not considered to be "ideal." Characteristics may include advanced donor age, prior infection with hepatitis B or hepatitis C, hypertension or diabetes mellitus, abnormal donor organ function, and non-heartbeating status of a cadaveric donor. The term "expanded" is used because an expansion of the donor pool is considered to increase transplantation and is preferred over the term "marginal donor."

Final Rule
The Organ Procurement and Transplantation Network Final Rule (42 CFR Part 121) was issued and published in the Federal Register on April 2, 1998. This rule governs the operation of the Organ Procurement and Transplantation Network and was amended (resulting from the Institute of Medicine's report, Organ Procurement and Transplantation, 1999). It was issued and published in the Federal Register on October 20, 1999. The Final Rule went into effect on March 16, 2000.

Graft
In the context of transplantation, a "graft" is an organ or tissue transplanted from one individual to another of the same species (e.g., human to human).

Graft Survival
Graft survival refers to whether a graft (i.e., an organ) is still functioning at a certain time point posttransplant. The time points used in the Annual Report tables include three months, one year, three years, and five years. Ten-year graft survival is also reported in Table 1.13.

Haplotype
One of a pair of three linked tissue-matching genes that are inherited as a unit.

Health Resources and Services Administration (HRSA)
HRSA, an agency of the United States Department of Health and Human Services, is charged with oversight of the Office of Special Programs, which in turn provides oversight to the Division of Transplantation. The mission of HRSA is to improve the nation's health by assuring equal access to comprehensive, culturally competent, quality health care for all. The goal is to assure total access health care and to eliminate health disparities for all Americans. HRSA supports a nationwide network of 643 community and migrant health centers and 144 primary care programs for the homeless and residents of public housing, serving 8.1 million Americans each year. HRSA also works to build the health care workforce and maintains the National Health Service Corps, oversees the nation's organ transplantation system, helps provide health resources for medically under-served populations, works to decrease infant mortality and improve child health, and provides services to people with AIDS through the Ryan White CARE Act programs. In the fiscal year beginning October 1, 2000, Congress appropriated $6.23 billion to HRSA, including $1.3 billion to provide primary health care in underserved areas, $1.8 billion to care for underserved people with HIV/AIDS, $964 million for services that improve maternal and child health, and $352 million to health professions training and quality assurance.

HHS
Department of Health and Human Services.

Histocompatibility Antigens
See Human Leukocyte Antigen System (HLA System), below.

HLA
Human Leukocyte Antigens. See Human Leukocyte Antigen System (HLA System), below.

HRSA
Health Resources and Services Administration.

Human Leukocyte Antigen System (HLA System)
Human Leukocyte Antigens (HLA), also known as histocompatibility antigens, are molecules found on all nucleated cells in the body. Histocompatibility antigens help the immune system to recognize whether or not a cell is foreign to the body. These antigens are inherited from one's parents. Human leukocyte antigens are used to determine the compatibility of kidneys and pancreata for transplantation from one individual to another. The major groups of HLA antigens are HLA-A, HLA-B, and HLA-DR. The values shown in this report are based on the six HLA antigens (two each for the A, B, and DR loci) reported for both donors and recipients. Tables reporting the level of HLA mismatch indicate the number of HLA antigens found in the donor that are not shared by the recipients. Generally speaking, the fewer the number of HLA mismatches the better the compatibility between donor organ and recipient.

Immunosuppression
The suppression of the immune response, usually with medications, to prevent the rejection of a transplanted organ or tissue. Medications commonly used to suppress the immune system after transplantation include prednisone, methylprednisolone, azathioprine, mycophenalate mofetil, cyclosporine, tacrolimus and sirolimus, among others.

Informed Consent
The process of agreeing to accept a medical test, procedure, or treatment. Informed consent is based on (a) full disclosure of the nature, risks, and benefits of the intended medical intervention; (b) comprehension of the disclosed elements; (c) competence to make an independent decision; and (d) freedom from coercion to allow for a truly voluntary response.

Justice
As applied to the medical ethics of transplantation, justice refers to allocation of organs to those patients in the most immediate need. Issues of justice are balanced by concerns of utility that, in this context, refer to allocating organs to those individuals who will make the "best" use of them. An example would be whether a potential recipient facing imminent death without a transplant but with a poorer chance of long-term survival should be given a transplant in preference to another individual with less immediate risk of death but a better long-term prognosis.

Living Donor
Living persons who donate organs for transplantation, including a kidney or a segment of the lung, liver, pancreas, or intestine. Living donors may be blood relatives, emotionally related individuals, or altruistic strangers.

Median Time to Transplant
This statistic is useful for candidates at the time they are first put on the waiting list. It reports the time at which half of the candidates will have received a transplant, among all those initially listed. If more than half of candidates are removed or die before receiving a transplant, or if the time is longer than the longest time available for the candidates included in the calculation, then this statistic is not reported. This median time to transplant considers all candidates who are initially registered on the waiting list and is generally longer than the median waiting time.

Median Waiting Time
This statistic reports the time at which half of the candidates registered on the waiting list would receive a transplant, if they remained active on the waiting list. It is calculated using the successive rates of transplantation seen at each time after registration, among candidates who remain active on the waiting list (dropping candidates when they die or are removed from the waiting list and excluding inactive
Times). This time is generally shorter than the median time to transplant since it uses transplant rates among those who remain active on the waiting list.

Medical Urgency Status Codes
Each candidate on the liver and heart waiting lists is assigned a status code which corresponds to how medically urgent it is that he or she receives a transplant. Medical urgency status for liver and heart is reported in the waiting list, recipient, and survival tables. Listed below are the definitions for each code, covering the last 10 years.

MELD
Model for End-Stage Liver Disease.

Model for End-Stage Liver Disease (MELD)
Uses three laboratory values (bilirubin, creatinine and INR) to calculate a score, on a scale of zero to 40, associated with the risk of death within three months on the liver waiting list.

National Organ Transplant Act (NOTA)
The National Organ Transplant Act (1984 Public Law 98-507), approved October 19, 1984 and amended in 1988 and 1990, provided for the establishment of the Task Force on Organ Transplantation; authorized the Secretary of HHS to make grants for the planning, establishment, and initial operation of qualified OPOs; and established the formation of the OPTN and Scientific Registry of Transplant Recipients (SRTR).

NOTA
National Organ Transplantation Act.

OPO
Organ Procurement Organization.

OPTN
Organ Procurement and Transplantation Network.

Organ Preservation
Between procurement from a donor and transplantation into a recipient, organs require special methods of preservation. The length of time that organs and tissues can be kept outside the body varies, depending on the organ, the preservation fluid, and the temperature.

Organ Procurement
The process of donor screening, and the evaluation, removal, preservation, and distribution of organs for transplantation.

Organ Procurement and Transplantation Network (OPTN)
Under a contract from HRSA and with oversight from the DoT, the OPTN operates the national network for organ procurement and allocation and works to promote organ donation. The current OPTN contractor is the United Network for Organ Sharing (UNOS), based in Richmond, Virginia.

Organ Procurement Organization (OPO)
An organization designated by CMS and responsible for the procurement of organs for transplantation and the promotion of organ donation. There currently exist 59 certified OPOs operating in the United States; each is a separate, private, nonprofit organization with its own board of directors.

Panel Reactive Antibody (PRA)
The percent PRA value is a measure of a patient's level of sensitization to donor antigens. It is the percentage of cells from a panel of blood donors against which a potential recipient's serum reacts. The PRA reflects the percentage of the general population that a potential recipient makes antibodies (is sensitized) against. The higher the PRA, the more sensitized a patient is to the general donor pool, and thus the more difficult it is to find a suitable donor. A patient may become sensitized as a result of pregnancy, a blood transfusion, or a previous transplant.

Patient Survival
Patient survival refers to whether a transplant recipient is still alive at a certain time point posttransplant. The time points used in the Annual Report tables include three months, one year, three years, and five years. Ten-year patient survival is also reported in Table 1.13.

Percentile
Used in the Annual Report referring to time to transplant. The Nth percentile measure is the value at which N% of the cases are at or below that value. For instance, for liver waiting list registrations in 1998, the 25th percentile is 140 days. This means that by 140 days after registration, 25% of these registrants had been transplanted. For the same group, the median is 390 days. The median is defined as the 50th percentile. For this group of liver registrants, 50% had been transplanted by 390 days.

PRA
Panel Reactive Antibodies.

Procurement
The process of donor screening and the evaluation, removal, preservation, and distribution of organs, tissues, or cells for transplantation.

Race
For purposes of this report, race and ethnicity are defined separately, as reported on the data collection forms. The two are not mutually exclusive. Race includes the following categories:

• White
• Black (listed as Black or African American)
• Asian (listed as Asian, Native Hawaiian, or other Pacific Islander)
• Other (listed as American Indian or Alaskan Native, Mid-East or Arabian, or Indian Sub-Continent)

Recipient
A transplant patient who receives an organ.

Rejection
A phenomenon that occurs when the immune system attacks a transplanted organ, tissue, or cell. Immunosuppressive drugs help prevent rejection.

Scientific Registry of Transplant Recipients (SRTR)
The SRTR provides analytic support for the ongoing evaluation of the scientific and clinical status of solid organ transplantation in the United States. With oversight and funding from the Division of Transplantation (DoT), the SRTR is currently administered, in collaboration with the University of Michigan, by the University Renal Research and Education Association (URREA).

Sensitization
Potential recipients are "sensitized" if there are antibodies in their blood against potential donors. Sensitization usually occurs as a consequence of pregnancy, blood transfusions, or previous transplantation. The degree of sensitization is measured by PRA. Highly sensitized patients are more likely to reject an organ transplant than are unsensitized patients.

SRTR
Scientific Registry of Transplant Recipients.

Standard Error
The standard error measures the level of precision associated with the estimate of the mean of a population. In this report, the "mean" refers to transplant survival rates. Categories that include a large number of transplants generally have small standard errors, while categories with relatively few transplants generally have large standard errors. Survival rates associated with a smaller standard error are more precise than those associated with a larger standard error. Standard errors are presented in the graft and patient survival rates tables.

Thoracic Organs
Organs located in the chest, i.e., the heart and lungs.

Time to Transplant
The time between when a patient is registered on a waiting list and when that patient receives a transplant. Annual Report tables show the median and other percentiles of time to transplant. The median time to transplant is the time by which 50% of a group of registrants have received a transplant. Among the factors affecting time to transplant are the shortage of organs; biologic issues such as blood type, body size of donors and recipients, PRA, immunological factors, and medical urgency status (for liver and heart); donation rates within an area; donation request and consent procedures at OPOs; and patient registration and organ acceptance practices at transplant centers. Table 1.6 presents an alternative measure, "waiting time before transplant," in which inactive time on the waiting list is not counted and patients are censored at any removal from the waiting list.

Tissue Type
An individual's combination of HLA antigens is called his/her tissue type. Matching for tissue type is important in kidney and pancreas transplantation. The tissue type for each patient on the waiting list is entered into a central computer maintained by the OPTN.

Transplant Center
A medical institution within the United States that operates an organ transplant program.

Transplant Program
Components of a transplant center. An individual transplant center may have programs for the transplantation of heart, lung, liver, kidney, pancreas, and/or intestine.

Tumor
An abnormal growth of tissue resulting from an uncontrolled multiplying of cells and serving no physiological function. Tumors can be either malignant (cancerous) or benign (non-cancerous). Malignant tumors include newly developed or "de novo" solid tumors as well as recurrent tumors that had been successfully treated previously. Posttransplant lymphoproliferative disorders (PTLD) are abnormal accumulations of immune cells and can be brought about by the immunosuppression therapies used to reduce organ rejection.

United Network for Organ Sharing (UNOS)
Located in Richmond, Virginia, UNOS is a private, nonprofit organization that holds a contract from the Health Resources and Services Administration of the U.S. Department of Health and Human Services to operate the OPTN. Through its policies, the OPTN ensures that all patients have a fair chance at receiving the organ they need, regardless of age, sex, race, lifestyle, religion, or financial or social status. The UNOS Organ Center matches organ donors to waiting recipients.

University Renal Research and Education Association (URREA)
Located in Ann Arbor, Michigan, URREA is a private, nonprofit organization established for the purpose of collecting information and conducting worldwide epidemiological, clinical, and economic studies of organ failure and related diseases. URREA's mission is to conduct research, to distribute information focused on improving patient care, and to provide analysis and research training opportunities for medical professionals. URREA, in collaboration with the University of Michigan, is responsible for the administration of the Scientific Registry of Transplant Recipients (SRTR).

UNOS
United Network for Organ Sharing.

URREA
University Renal Research and Education Association.

Utility
As applied to the medical ethics of transplantation, utility refers to allocating organs to those individuals who will make the "best" use of them. Issues of utility are balanced by concerns for justice that, in this context, refer to allocation of organs to those patients in the most immediate need. An example would be whether a potential recipient facing imminent death without a transplant but with a poorer chance of long-term survival should be given a transplant in preference to another individual with less immediate risk of death but a better long-term prognosis.

Ventricular Assist Device (VAD)
A mechanical pump that is implanted into a patient with heart failure to maintain blood circulation; it is used as a bridge to heart transplantation.

Waiting List (registration, active, inactive, removal)

After evaluation by a team of transplant professionals, a patient is added to the national waiting list by the transplant center. Lists are specific to both geographic area and organ type: kidney, pancreas, kidney-pancreas, liver, intestine, heart, lung, and heart-lung. Each time a donor organ becomes available, a computer generates a list of potential recipients based on factors that may include genetic similarity, organ size, medical urgency, and time on the waiting list. Through this process, a new list that best matches a waiting patient to a donated organ is generated each time an organ becomes available.

Active - A patient who does not have any contraindications to transplantation at the current time and is actively awaiting transplantation.

Inactive - Patients can be placed on inactive status if they temporarily are not appropriate candidates for transplantation (e.g., active infection, etc.).

Removal - A patient can be removed from the waiting list voluntarily, or if he/she becomes too ill to withstand or benefit from transplantation, achieves a spontaneous recovery of organ function, is transplanted, or dies.