Dear Doctor Column, April 21, 2003
Question:
How are blood donors screened and what tests are performed on donated blood? What are the requirements for giving blood, how often can you donate, and how safe is it to give or to receive blood? Also, please explain what a universal donor is. Thank you for your time.
Answer:
The questions you ask are some of the most common received by blood banks about blood donation. These are good questions and we appreciate you sending them to us.
According to the American Association of Blood Banks, about 14 million units of blood are donated every year in the U.S. by about 8 million volunteer donors. This supply of blood is used by 4 million patients, including accident victims, people undergoing surgery, and patients with leukemia, cancer, and other diseases. Just one pint of donated blood can help save three lives.
To give blood, you must be at least 17 years old and weigh at least 110 pounds. All donors also must pass the physical and health history examination. Each donation requires approximately 1 to 2 hours of your time. You can donate blood about every 56 days, or 6 times a year.
Blood from potential donors is tested for ABO group (blood type) and Rh type (positive or negative). Screening tests also are performed to detect infection with hepatitis viruses B and C, human immunodeficiency virus (HIV), human T-lymphotropic viruses (HTLV), and syphilis. In addition to these tests, a special test called nucleic acid testing (NAT) is capable of detecting HIV and hepatitis C viruses early in the infection, before a blood donor's immune system has begun to produce antibodies against them, which is what the standard HIV and hepatitis C virus tests measure. In all, 14 tests are performed on every unit of donated blood; 11 of these tests, including NAT, are for infectious diseases.
Because these screening tests are so sensitive, some donors may have a false-positive result, which means the test is positive even though the person does not have the disease. To sort out true infections from false-positive tests, more specific tests, called confirmatory tests, are necessary. If the test result from a donated unit of blood is abnormal for any of these disease markers, the unit is discarded, and the potential donor is notified.
Individuals who are disqualified as blood donors are said to be "deferred." Whether a person is deferred temporarily or permanently depends on the reason for the disqualification. For example, a person may be deferred temporarily because of anemia, which is usually reversible with treatment.
The nation's blood supply is safer today than it has ever been and is as safe as modern science and medicine can make it. You cannot acquire any disease through donating blood because new, disposable, sterilized equipment is used for each donation. It also is safe to receive a blood transfusion. In fact, the risks of contracting a blood-borne disease through transfusion are far less than the risks of not receiving that transfusion at all. For example, the American Red Cross reports that the chance of contracting the virus that causes AIDS through a blood transfusion is 1 in 1.5 million.
The distribution of blood types in the U.S., from most common to least common are:
O Rh-positive 38%
A Rh-positive 34%
B Rh-positive 9%
O Rh-negative 7%
A Rh-negative 6%
AB Rh-positive 3%
B Rh-negative 2%
AB Rh-negative 1%
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. Blood centers often run short of type O and type B blood, and shortages of all types of blood occur during the summer and winter holidays.
As a special benefit to the donor, many blood collection centers will check your cholesterol level, and the results will be mailed to you within a few weeks of your donation. Also, a blood type identification card will be mailed to first-time donors, or by request. This card is something you should carry at all times. Knowing your blood type in an emergency can easily save your life.
If you are interested in donating blood, contact one of the following organizations for more information and to find out where you can schedule an appointment to donate: