Blood donation, also called blood banking, refers to the process of collecting, testing, preparing, and storing whole blood and blood components intended primarily for transfusion . Blood donors are typically unpaid volunteers, but they may also be paid by commercial blood donation and processing enterprises, such as independent blood banks and donor centers. Blood registry refers to the collection and sharing of data about donated blood and donors. Donors who have been determined to be temporarily or permanently ineligible to donate blood are listed in a confidential national data base known as the Donor Deferral Register. The quality and safety of the U.S. blood supply is governed by physician-established guidelines for the practice of blood banking as found in the Standards of the American Association of Blood Banks (AABB) and through the organization's inspection and accreditation program. The Food and Drug Administration (FDA) controls federal licensure of blood banks. Hospital blood banks are also inspected by The College of American Pathologists (CAP) and the Joint Commission on Accreditation of Healthcare Organizations (JCAHC).
Blood is collected, processed, stored, and distributed to maintain an adequate supply of whole blood and blood components for transfusion as needed. Blood replacement may be needed by people who have lost blood through accidents, burns, hemorrhage, or surgery. Blood or blood components are also used in the treatment of certain types of anemia, various disease conditions, and for medical research.
Healthy donors may be called upon to donate periodically to help maintain the overall blood supply or when their specific blood type is needed. People may sometimes donate blood to benefit a specific person. Directed donor blood is reserved for an intended recipient, such as a family member or friend; it is tested and processed as all other donated blood to ensure that it is appropriate for the recipient. People preparing for elective surgery may have their blood collected and held, and then returned to them if needed during their surgery. This process is known as autologous blood donation . Donors are advised to give blood only once in an eight-week period to maintain the iron stores in their blood. Autologous donors may donate more often if it is determined by their physician to be to their benefit.
The National Blood Data Resource Center reports that about 13.9 million units of whole blood (one unit of whole blood equals 450 ml, or about 1 pt) are donated annually in the United States, of which about 695,000 are autologous donations for elective surgery. The country's blood supply is donated by about eight million people, representing a broad cross section of the population, although fewer than 5% of those eligible donate. About half of the total amount needed is processed, stored, and delivered by the 36 regional blood centers of the American Red Cross; hospital blood banks, community blood centers, mobile blood drives, and independent blood banks collect, process, and distribute the other half.
Blood is donated as whole blood, collected in a plastic bag containing an anticoagulant that will keep the blood from clotting and allow it to be separated into multiple components. By dividing blood into components that each offer different clinical benefits, one unit of donated blood can meet the transfusion needs for more than one person. This practice is essential to meet the constant demand for blood; every year in the United States, more than four million people require blood transfusions. About 26 million transfusions are administered either as whole blood or components that have been prepared from whole blood. About 34,000 units per day, for example, are transfused as red cells.
Whole blood and blood components are used in various ways to meet the clinical needs of recipients. Whole blood is sometimes used to replace blood volume when a significant amount of blood has been lost through accidents or surgery. Red blood cells, which carry oxygen, are used to treat certain anemias and are often the preferred component when multiple transfusions are being administered to one person, as in open heart surgery or organ transplants. Platelets, part of the complex coagulation (clotting) system that helps control bleeding, are commonly used in the treatment of acute leukemia and some types of cancer. Fresh frozen plasma, which contains critical coagulation factors, is used to control bleeding in people who lack these factors. Cryoprecipitated (prepared from frozen plasma) antihemophilic factor (AHF) is transfused to provide a specific coagulation factor that is deficient in hemophilia and other diseases. Blood for transfusion is requested by physicians. Pre-transfusion testing and issuance of blood and components to the recipients is performed by a transfusion service, which is commonly provided or supervised by a hospital blood bank.
The actual process of donating whole blood takes about 20 minutes. The donor will either lie down or will sit in a special donor chair that elevates the lower body and legs. After selecting an appropriate vein, the phlebotomist (an individual trained in blood collection technique) will clean the arm well at the site of the needle puncture (venipuncture). With a tourniquet tightly in place on the donor's arm, a sterile needle is inserted into a vein. As the tourniquet is released, blood flows through plastic tubing into a plastic blood bag. The donor may be asked to open and close a fist to encourage blood to flow. Usually only one unit of blood is collected. Pressure is applied to the site of the venipuncture until the blood flow has been stopped. Donors are then escorted to an observation area, given light refreshments that include liquid, and allowed to rest. Positive identification of the donor and the blood bag from that donor are essential. The same unique identification number is assigned to the
Plasma, the liquid portion of whole, anticoagulated blood in which blood cells, coagulation factors, and other blood constituents are suspended, is also collected. This is often done by commercial enterprises that sell it to companies manufacturing clotting factors and specific plasma protein products, or to companies and institutions engaged in medical research. Plasma is collected using a process known as apheresis, in which whole blood is collected, the desired blood component is removed, and the remainder is returned to the donor. Collecting plasma generally takes one to two hours. Apheresis may also be used to collect other blood components, such as platelets and granulocytes.
Different blood components vary in how long they can be stored. Red blood cells can be refrigerated for up to 42 days or coated with a protective agent and frozen at extremely low temperatures in liquid nitrogen, a process that preserves them for up to 10 years. Platelets must be used soon after they are prepared; they are stored at room temperature for no more than five days. Fresh frozen plasma and cryoprecipitated AHF can be kept for as long as one year.
To ensure the safety of the blood supply, a multi-tiered process of donor screening and deferral is employed. This involves donor education, taking a detailed health history of each prospective donor, and giving potential donors a simple physical examination , which includes measuring blood pressure and pulse rate, taking a few drops of blood to test for hemoglobin, the iron-bearing protein in blood, and also measuring blood cell volume. These tests will indicate general health and help ensure that donation will not contribute to anemia in the donor. At any point in the process, a potential donor may be "deferred," or determined to be ineligible to donate blood. This deferral may be temporary or permanent, depending on the reason. Potential donors are also encouraged to "self-defer," or voluntarily decline to donate, rather than put future blood recipients at risk.
In general, blood donors must be at least 17 years old (some states allow younger people to donate blood with their parents' consent), must weigh at least 110 lb (50 kg), and must be in good health. Donors with a history of heart, lung, or liver disease or who are pregnant are usually deferred. Donors can be disqualified if they are known to have engaged in behavior that put them at risk of infection (such as having had a tattoo, having had sex with people in high-risk groups, having used illegal intravenous drugs, having had certain diseases, or having been raped) or have spent time in specific parts of the world, such as areas where malaria may be prevalent.
All donated blood is extensively tested before being distributed for use by transfusion services. The first step is determining the blood type, which is the primary indication of who can receive the blood. Blood is also screened for any irregular antibodies that could cause complications for the recipients. In addition, donor blood is screened for infectious diseases, such as hepatitis, AIDS, and syphilis, by testing for specific markers of these diseases that will appear in the blood of those infected. These include: Hepatitis B surface antigen (donors with this antigen are immune and can be accepted), hepatitis B core antigen, hepatitis C virus antibody, HIV-1 and HIV-2 antibodies, HIV p24 antigen, and HTLV-I and HTLV-II antibodies. Other tests may be performed if a recipient's doctor requests them.
In order to detect the greatest possible number of infections, when present at even the lowest levels in donor blood, these screening tests are extremely sensitive. For this reason, however, donors sometimes receive false positive test results. In these cases, more specific confirmatory tests are performed to help rule out false positive results. Blood found to be not suitable for transfusion is discarded, and all items coming into direct contact with donors are used only once and then discarded. Donors of infected blood are entered into the Donor Deferral Register to prevent subsequent donation of their blood at other blood donation facilities.
There are eight major blood types comprising four ABO groups (A, B, AB, and O), and the presence or absence of the Rh factor, designated as either type Rh positive (+) or type Rh negative (-). These types and their approximate distribution in the U.S. population are as follows: O+ (38%), O- (7%), A+ (34%), A- (6%), B+ (9%), B- (2%), AB+ (3%), AB- (1%). In an emergency, when there may be no time for compatibility testing, anyone can safely receive type O red blood cells, and people with this blood type are known as "universal donors." People with type AB blood, known as "universal recipients," can receive any type of red blood cells and can give plasma to all blood types. Receiving the wrong blood type can result in the destruction of red cells in the recipients body and even death. For this reason, the transfusion service must conduct more pre-transfusion testing to determine the compatibility of the donor blood with the blood of the recipient. This compatibility testing, known as type and cross match, begins with matching the major blood types. Additional testing will include antibody screening of the recipient and, if specific antibodies are found, testing of other blood groups (the MN group or Kell and Lewis groups, for example) will be done to find compatible donor blood.
Thanks to the use of a multi-tiered donor screening system and advances in the effectiveness of screening tests, the risk of transmitting infectious diseases to recipients via transfusion has been significantly diminished. Nonetheless, there is still a minuscule risk that blood recipients could contract human immunodeficiency virus (HIV), hepatitis, or other diseases via transfusion. Other diseases that are of particular concern to blood-collection agencies include: babesiosis, Chagas disease, human T-lymphotropic virus (HTLV-I and -II), cytomegalovirus (CMV), Lyme disease, malaria, Creutzfeldt-Jakob disease, and new variant Creutzfeldt-Jakob disease.
There are few risks to healthy donors when AABB standards for donation are followed. People who donate blood replace the fluid they lose within 24 hours and the red cells within two months. A person can safely donate blood once in eight weeks. Donors' blood will be tested prior to donation to determine their eligibility; those ineligible will be advised of the temporary or permanent reasons for being disqualified. Their names will be placed on the national deferral registry to prevent donation at other sites and to help protect the blood supply.
Medical professionals who draw the blood of eligible donors will advise donors of any necessary precautions following donation. Most blood donors suffer no significant after effects. Occasionally donors may feel faint or dizzy, nauseous, or have tenderness, redness, or a bruise where the needle was inserted to draw their blood. More serious complications, which rarely occur, may include fainting, muscle spasms, or nerve damage.
AABB standards are designed to protect donors and recipients and especially to help ensure that compatible blood is transfused to each recipient. The accurate labeling of blood, blood components, and donor records, and the recording of all data is essential from the time blood is collected, through testing and preparation, and through pre-transfusion testing and issuance of the blood or blood component. Autologous blood donors run a tiny risk of having the wrong blood returned to them due to clerical error. There is also a faint possibility of bacterial contamination of the autologous blood. These rare occurrences apply to all other transfusions as well.
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American Association of Blood Banks. 8101 Glenbrook Road, Bethesda, MD 20814-2749. (301) 907-6977. http://www.aabb.org .
American Red Cross. 430 17th Street NW, Washington, D.C. 20006. http://www.redcross.org .
National Blood Data Resource Center. (301) 215-6506. http://www.nbdrc.org .
Peter Gregutt L. Lee Culvert