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Fast facts on blood
Tuesday, September 01, 1998
What is the most common blood type?
Here's the approximate distribution of blood types in the U.S. population:
O, Rh-positive - 38 percent
O, Rh-negative - 7 percent
A, Rh-positive - 34 percent
A, Rh-negative - 6 percent
B, Rh-positive - 9 percent
B, Rh-negative - 2 percent
AB, Rh-positive - 3 percent
AB, Rh-negative - 1 percent
In an emergency, anyone can receive type O red blood cells, and type AB individuals can receive red blood cells of any ABO type. Therefore, people with type O blood are known as "universal donors" and those with type AB blood are known as "universal recipients." In addition, AB plasma donors can give to all blood types.
What tests are performed on donated blood?
After blood is drawn, it is tested for blood type and Rh type (positive or negative), as well as for any unexpected red blood cell antibodies that may cause problems in the recipient. Screening tests also are performed for evidence of infection with hepatitis viruses B and C, human immunodeficiency virus 1 and 2, human T-lymphotropic viruses I and II and syphilis.
The blood bank by certified letter notifies donors who test positive for any of these conditions.
How is blood stored and used?
Each unit of blood is separated into several components. Red blood cells may be refrigerated for up to 42 days or frozen for up to 10 years. Red cells carry oxygen and are commonly used to treat anemia.
Platelets are important in the control of bleeding and are generally used in patients with leukemia and other forms of cancer. Platelets are stored at room temperature and may be kept for up to five days.
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