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Your Link to Life |
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Blood Testing:
The Seventh Line of Safety
The American Red Cross performs nine laboratory
tests for nine different infectious disease markers on every unit of donated
blood. Seven of those markers were added between 1985 and 1999 to further ensure
the safety of the blood supply.
More than three million tests are performed on
blood donated in the New York-Penn Region each year. The Red Cross actively
researches new disease-causing agents and is committed to adding new tests as
they become available. Additionally, tests currently in use are upgraded
regularly as improvements in the tests are released.
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Syphilis (STS) (late 1940's) Detects
the presence of antibodies that are produced when a person has syphilis, a
contagious venereal disease. No cases of transfusion-transmitted syphilis have
been recorded for more than 30 years, in part because the organism does not
survive storage at refrigerated temperatures.
Hepatitis B Surface Antigen (HbsAg) (Early
1970's) Detects material on the surface
of the hepatitis B virus itself. The current risk of transfusion-transmitted
hepatitis B is 1 in 200,000. (This compares to the overall incidence in the
general population of 1:250)
Human Immunodeficiency Virus, Types 1 and 2 (HIV
1,2) (March 1992) Detects antibodies
produced by the body in response to infection with either or both HIV-1 or
HIV-2, viruses that cause AIDS. The test for HIV-1 was first introduced in March
1985, and has been regularly upgraded since, with the latest upgrade being a
combination test that also screens for HIV-2, which is found primarily in parts
of Africa below the Sahara Desert. The current risk of contracting AIDS from a
unit of blood is 1 in 450,000 to 660,000. Before 1985 that risk was one in every
2,600.
Alanine Aminotransferase (ALT) (September 1986)
Measures a normal liver enzyme. Elevated levels may be a sign of liver
inflammation, commonly caused by hepatitis. The test measures the consequence of
liver inflammation rather than the presence of a particular hepatitis virus. Use
of this screening test exceeds FDA requirements. An ALT elevation may not mean
the donor has any medical abnormality.
Hepatitis B Core Antibody (Hbc) (November 1986)
Detects antibodies produced by the body in response to infection with the
hepatitis B virus. Used to identify individuals whose life experiences may have
placed them at increased risk to carry a transfusion transmissible disease.
Human T-Lymphotropic Virus (HTLV-I) (December
1988) Detects antibodies produced by the
body in response to infection with HTLV-I, a virus that causes a rare form of
leukemia or paralysis. Also will detect antibodies to a related virus, HTLV-II.
Hepatitis C Virus (HCV 2.0) (March 1992)
Detects antibodies produced by the body in response to infection with the
hepatitis C virus. Since its introduction in 1990, the test has been upgraded to
be even more sensitive.
Human Immunodeficiency Virus (HIV-1 p24 Antigen
Assay) (March 1996) The HIV antigen test
is a marker for the virus' own proteins. The test is expected to decrease the
"window period" (the time between infection and reaction to available
tests), by about one third, from 22 days to approximately 12-16 days. This test
will reduce the estimated risk of contracting HIV from a blood transfusion to
one in 676,000.
Nucleic Acid Testing (NAT) (June 1999) Uses
a new form of testing technology that can directly detect the genetic material
of transfusion transmitted viruses, such as HIV, the virus that causes AIDS, and
hepatitis C (HCV). All of the blood collected by the Red Cross for transfusion
is now subjected to NAT under an Investigational New Drug application submitted
to the FDA.
In addition to these tests, the Red Cross
tests every unit to identify significant characteristics of a donor’s blood,
such as the donor’s blood group (O, A, B or AB) and Rh type, and screens for
atypical or unusual red cell antibodies. |