Use this information to answer the question. Human Immunodeficiency viruses, Types 1 and 2 (HIV 1,2) Antibody testing (1985) and NAT (1999) Blood donation screening for HIV-1, the causative agent of AIDS began with antibody testing in 1985. Many improvements in testing have occurred including adding the detection of a second HIV agent (HIV-2 in 1992). A chemiluminescent immunoassay (ChLIA) is used for the qualitative detection of antibodies to HIV-1 and HIV-2. A duplex nucleic acid test (NAT) was introduced for HIV-1/HCV RNA detection in 1999, and updated to include the detection of HBV DNA in 2009 (see above). The next version of NAT will include HIV-2 RNA detection (to be implemented in 2020). Donors who test antibody reactive are further evaluated by additional tests to confirm the presence of HIV antibody and to differentiate HIV-1 from HIV-2 antibodies. Tests for this purpose have included a HIV western blot, an HIV-2 enzyme-linked immunoassay and an HIV-1 and HIV-2 rapid test for viral differentiation (all FDA licensed). Donors testing falsely positive by either antibody or HIV NAT may be reentered. The per unit risk of HIV-1 infection through blood transfusion is less than 1 per 2 million units screened. NAT closes the window period between infection and the detection of antibody for those infected with HIV by about 2 weeks. This leaves an approximate period of 7 to 10 days when an infected donor may not be detected by blood donation screening. The frequency of detecting HIV-1 in a blood donor is about 1 per 33,000 donations screened; however, the frequency of detecting HIV-2 in a blood donor is extremely rare at 1 per 57 million donations with only 5 such infected donors ever identified since HIV-2 screening began in 1992. Why is NAT testing used for HIV compared to traditional serology testing?
Use this information to answer the question.
Human Immunodeficiency viruses, Types 1 and 2 (HIV 1,2) Antibody testing (1985) and NAT (1999)
Blood donation screening for HIV-1, the causative agent of AIDS began with antibody testing in 1985. Many improvements in testing have occurred including adding the detection of a second HIV agent (HIV-2 in 1992). A chemiluminescent immunoassay (ChLIA) is used for the qualitative detection of antibodies to HIV-1 and HIV-2. A duplex
Why is NAT testing used for HIV compared to traditional serology testing?
The ultimate diagnosis of HIV infection at any age requires diagnostic testing that confirms the presence of HIV. Generally, tests are helpful for individual diagnosis, protection of blood or tissue products, safety and public health surveillance. However, the most suitable test is chosen based on convenience and characteristics of test characteristics, and also the population to whom the testing belongs. As far testing is concerned, a highly sensitive test is used for screening, followed by a highly specific test for confirmation.
Serology refers to using antigen-antibody reactions in the laboratory for diagnostic purposes. The liquid portion of the blood where antibodies are found is known as serum which is used in testing. Serological testing identifies HIV antigen and/or antibody generated as part of the immune response to infection with HIV. Serologic testing may be used in the in two distinct ways:
a.To identify unknown antigens i.e., microorganisms). This process is called direct serologic testing. It uses a preparation of known antibodies called antiserum, to identify an unknown antigen.
b. To detect antibodies made against a specific antigen in the patient's serum. This is called indirect serologic testing. Indirect serologic testing is the process by which antibodies in a person's serum being made by that individual against an antigen associated with a particular disease are detected using a known antigen.
Antigen-antibody reactions may be detected in the laboratory by a variety of techniques. Some of the commonly used techniques for observing in vitro antigen-antibody reactions are agglutination, precipitation, ELISA, etc.
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