Types of HIV Tests
The body makes antibodies to try to fight HIV, although the antibodies cannot eradicate the virus. Antibody testing is often done in two parts. First a sensitive screening test is performed on the blood. If the screening test is positive, a second test is done to confirm that HIV antibodies are present. The types of tests have varied over the years. At first, the screening test used an enzyme-linked immunoassay (ELISA) with confirmatory testing by Western blot. This strategy did not test for HIV-2, sometimes misclassified HIV-2 infection, missed very early infections where antibody had not yet been produced, and sometimes produced indeterminate results. Scientists developed newer tests to address these issues. Other tests took hours or days to return results, requiring people to return to the clinic. Rapid HIV tests (such as Clearview) were developed that could provide results during the initial visit. Some tests can be done at home without the need for a clinic visit. For a self-test or home-test, the person buys a kit (for example, OraQuick), swabs the inside of their cheek, places the swab in the supplied fluid, and reads the results in a test window. Positive results indicate the need to visit a clinic for confirmatory testing.
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HIV (human immunodeficiency virus) testing facts
- HIV testing is done to diagnose those who are newly infected, to identify previously unrecognized infections, and to relieve the minds of those who are not infected.
- HIV testing should be a routine part of medical practice.
- It is critical that pregnant women be tested because medications are very effective in reducing transmission of HIV from mother to baby.
- HIV testing is usually a two-step process. The first step is to test for antibodies in blood or saliva. If the test is positive, a second test called a Western blot is done to ensure that the first result was correct.
- If both tests (antibody and Western blot) are positive, the chances are >99% that the patient is infected with HIV.
- HIV antibody tests may miss some infections, resulting in false-negative tests. This often occurs soon after infection when antibodies have not yet developed or are just starting to form and are at a level too low to be detected (within about four weeks of infection).
- There are free HIV testing locations in every state.
What is the human immunodeficiency virus (HIV)?
HIV is short for human immunodeficiency virus. This is the virus that causes the acquired immunodeficiency syndrome or AIDS. HIV is a complicated virus that uses RNA, not DNA, as its genetic messenger. It replicates (reproduces) primarily in specialized cells of the body's immune system called CD4 lymphocytes. During HIV replication, the CD4 cells are destroyed. As more and more cells are killed, the body loses the ability to fight many infections. If the number of CD4 cells in the bloodstream falls below 200 per cubic millimeter, or if some other special conditions occur, the person is defined as having AIDS. These special conditions include infections and cancers that take advantage of the way that HIV suppresses the immune system. Regardless of the CD4 count, people with HIV infection carry the virus and can spread it to others through unprotected sex or contact with blood or some other body fluids.
Statistics show that more than 1.1 million Americans are currently infected with HIV. Over 250,000 of these Americans are not aware that they are infected. The U.S. Centers for Disease Control and Prevention (CDC) estimates that more than 50,000 new infections with HIV occur each year. Thus, HIV testing is important to diagnose those who are newly infected, to identify previously unrecognized infections, and to relieve the minds of those who are not infected. HIV testing is also used to reduce the risk of transmission during blood transfusions and tissue transplantation.
The CDC recommends routine HIV testing of adolescent and adult patients aged 13 to 64 in all health-care settings, of all women during pregnancy and the newborns of HIV positive women. Thus, HIV testing is considered part of routine medical practice, similar to tests that screen for other diseases. People who are at high risk for acquiring HIV should be tested at least annually. Sometimes, doctors request or require testing as part of evaluation and treatment for other conditions, such as women undergoing treatment with assisted reproductive technologies for infertility or treatment of viral hepatitis. There is increasing concern that not enough people are being tested. Events such as National HIV Testing Day have been used to raise awareness and increase participation in testing.
In some cases, HIV testing may be required by law. This occurs for blood that is used for transfusions, organ donors, and military personnel. States may select additional populations for mandatory testing, such as prisoners or newborns.
Medically Reviewed by a Doctor on 3/23/2016