Answers
08/03/1989

<TITLE>New AIDS Antigen Test </TITLE>
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                               August 3, 1989 

                       NEW AIDS TEST DETECTS ANTIGENS 
    FDA today licensed the first diagnostic kit to detect the presence of 
Human Immunodeficiency Virus Type-1 (HIV-1) -- the AIDS virus -- by directly
detecting the proteins, or antigens, of the virus.  Previous kits have shown
the presence of the virus indirectly, by detecting the body's response -- 
the antibody -- to these proteins.  The new HIV-1 antigen test is approved
to help physicians diagnose and follow the medical status of HIV-1 infected 
individuals.  It is not recommended for use in screening blood or plasma
donations.
    The following may be used to answer questions:
    Unlike other enzyme linked immunoassay tests (ELISA) or the Western Blot
tests which have been approved for HIV-1 diagnosis and screening, this new
enzyme immunoassay detects HIV-1 viral antigens rather than antibodies that 
have developed in response to HIV-1 infection.  Antigens are proteins of the
virus itself, as opposed to antibodies which are compounds produced by the
body's immune system in response to the HIV-1 infection.
    A number of studies have demonstrated a correlation between detectable
levels of HIV-1 antigen and the appearance of symptoms and complications
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associated with the onset of AIDS Related Complex or full-scale AIDS. 
Therefore, the HIV-1 antigen test kit may help physicians monitor changes in
the medical condition of HIV-1 infected people.  This knowledge can help the
physician and patient determine whether the HIV-I infected patient might
be progressing to a more advanced state of disease and what type of therapy 
should be initiated.
    Since HIV-1 antibodies can take as long as 6 months or more to develop, 
and since HIV-1 antigens appear temporarily as early as two weeks after 
infection it was theorized that the HIV-1 antigen test in some cases might
detect the presence of HIV-1 at an earlier point after infection than HIV-1 
antibody tests. 
    This expectation was not borne out by extensive studies conducted in
this country and Europe which compared the effectiveness of HIV-1 antigen 
and antibody tests for screening whole blood donations.  These data were
presented at a meeting of FDA's Blood Products Advisory Committee on March
23, 1989.  This advisory committee of outside experts also reviewed data on 
the diagnostic use of the HIV-1 antigen test. 
    The committee voted against recommending the licensing of the antigen 
test as a screening test for blood donors, because the available evidence 
indicated that it does not significantly improve upon the reliability of
AIDS antibody tests already in use.  The committee also voted against 
recommending licensure of test for screening source plasma donors because 
viral inactivation procedures and HIV-1 antibody screening provide adequate 
safety for products prepared from source plasma.
    However, the committee did find the data on the efficacy of the HIV-1 
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antigen test kit for diagnostic and prognostic use to be convincing and 
recommended that FDA license the antigen test for use in  those patients who
are known to carry the AIDS virus.
    Although the committee's recommendations are not binding upon FDA, the
agency in its review of the product license application for the HIV-1 
antigen test agreed that the test should be licensed for diagnostic and 
prognostic use by health care professionals treating known HIV-1 infected 
individuals.
    Abbott Laboratories of Abbott Park, Ill., the developer of this HIV-1 
antigen test kit, will market the newly licensed test for use as a
diagnostic/prognostic test under the trade name HIVAG-1.
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