Blood Donations and Blood Banking
Blood banking is the process that takes place in a laboratory to ensure that the donated blood or blood products are safe before they are used in blood transfusions and other medical procedures. Blood banking includes typing the blood for compatibility and testing for infectious diseases.
- About 38,000 units of red blood cells are needed every day.
- The number of blood units donated is almost 15 million a year.
- There are approximately 8 million volunteer blood donors.
- About 4.9 million patients receive transfusions of blood units each year.
- Each unit of blood is broken down into components, such as red blood cells, plasma, and platelets. One unit of whole blood, once separated, may be transfused to several patients, each with different needs.
- Annually, more than 29 million units of blood components are transfused.
Most blood donors are volunteers. However, sometimes a patient may want to donate blood a couple of weeks before undergoing surgery, so that his/her blood is available in case a blood transfusion is necessary. Donating blood for yourself is called an autologous donation.
To further ensure the safety of the blood donation process and available blood supply, volunteer blood donors must pass certain criteria, including the following:
- must be at least 17 years of age
- must be in good health
- must weigh at least 110 pounds
- must pass the physical and health history examination given prior to donation
Some states permit persons younger than 17 years to donate blood with parental consent.
A certain set of standard tests are performed in the laboratory once blood is donated, including, but not limited to, the following:
- typing: ABO group (blood type)
- Rh typing (positive or negative antigen)
- screening for any unexpected red blood cell antibodies that may cause problems in the recipient
- screening for current or past infections including the following:
- hepatitis viruses B and C
- human immunodeficiency virus (HIV)
- human T-lymphotrophic viruses (HTLV) I and II
- West Nile virus
- Irradiation to blood cells is performed to disable any T-lymphocytes present in the donated blood. (T-lymphocytes can cause a reaction when transfused, but can also cause what is called "graft-versus-host" problems with repeated exposure to foreign cells.)
- "Leukocyte reduced blood" has been filtered to remove the white blood cells which contain antibodies that can cause fevers in the recipient of the transfusion. (These antibodies, with repeated transfusions, may also increase a recipient's risk of reactions to subsequent transfusions.)
According to the American Association of Blood Banks, distribution of blood types in the US includes the following:
- O Rh-positive - 38 percent
- A Rh-positive - 34 percent
- B RH-positive - 9 percent
- O Rh-negative - 7 percent
- A Rh-negative - 6 percent
- AB Rh-positive - 3 percent
- B Rh-negative - 2 percent
- AB Rh-negative - 1 percent
While blood or one of its components may be transferred, each component serves many functions:
- red blood cells - carry oxygen to the tissues in the body and are commonly used in the treatment of anemia.
- platelets - help the blood to clot and are used in the treatment of leukemia and other forms of cancer.
- white blood cells - help to fight infection, and aid in the immune process.
- plasma - the watery, liquid part of the blood in which the red blood cells, the white blood cells, and platelets are suspended. Plasma is needed to carry the many parts of the blood through the bloodstream. Plasma serves many functions, including the following:
- helps to maintain blood pressure
- provides proteins for blood clotting
- balances the levels of sodium and potassium
- cryoprecipitate AHF - a portion of the plasma that contains clotting factors that help to control bleeding.
Albumin, immune globulins, and clotting factor concentrates may also be separated and processed for transfusions.
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Online Resources of Hematology & Blood Disorders