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HIV/AIDS Testing

(The following information was obtained from the National HIV testing website; a service of the CDC.)

Types of HIV Tests

Antibody Test

The antibody test looks for the presence of antibodies produced by your body to fight off the HIV infection. When HIV enters the body, it begins to attack certain white blood cells called T4 lymphocyte cells (helper cells). Your doctor may also call them CD4 cells. The immune system then produces antibodies to fight off the infection. Although these antibodies are ineffective in destroying HIV, their presence is used to confirm HIV infection. Antibody tests look for the presence of HIV antibodies; they do not test for the virus itself.

Blood Tests

The most commonly used initial test is the blood test enzyme immune assay (EIA) or the enzyme-linked immunosorbent assay (ELISA). If EIA test results show a reaction, the test is repeated on the same blood sample. If the sample is repeatedly the same result or either duplicate test is reactive, the results are "confirmed" using a second test such as the Western blot. HIV testing consists of an initial screening with two types of tests commonly used to detect HIV infection. This more specific (and more expensive) test can tell the difference between HIV antibodies and other antibodies that can react to the EIA and cause false positive results. False positive EIA results are uncommon, but can occur. A person is considered infected following a repeatedly reactive result from the EIA, confirmed by the Western blot test.

In addition to the EIA or ELISA and Western blot, other tests now available include:

	Radioimmunoprecipitation assay (RIPA): A confirmatory blood test that may be used when antibody levels are very low or difficult to detect, or when Western blot test results are uncertain. An expensive test, the RIPA requires time and expertise to perform.
	Dot-blot immunobinding assay: A rapid-screening blood test that is cost-effective and that may become an alternative to standard EIA and Western blot testing.
	Immunoflourescence assay: A less commonly used confirmatory blood test used on reactive ELISA samples or when Western blot test results are uncertain.
	Nucleic acid testing (e.g., viral RNA or proviral DNA amplification method): A less available blood test that can be used to resolve an initial indeterminate Western blot result in certain situations.
	Polymerase chain reaction (PCR): A specialized blood test that looks for HIV genetic information. Although expensive and labor-intensive, the test can detect the virus even in someone only recently infected.

Do all HIV tests involve drawing blood?

No. Urine and oral-fluid HIV tests offer alternatives for anyone reluctant to have blood drawn.

Urine testing for HIV antibodies is not as sensitive or specific as blood testing. Available urine tests include an EIA and a Western blot test that can confirm EIA results. A physician must order these tests, and the results are reported to the ordering physician or his or her assistant.

Orasure© and OraQuick Advance HIV1/2 are currently the only FDA approved oral-fluid tests. Fluid is collected from inside the mouth and analyzed using an EIA test and supplemental Western blot test, if necessary. Oral fluid tests are offered at many HIV testing locations. Contact a location near you to find out if this test is available.

What are rapid HIV tests?

A rapid HIV test is a test that usually produces results in up to 20 minutes. In comparison, results from the commonly used HIV-antibody screening test, the EIA, are not available for 1-2 weeks.

There are currently four rapid HIV tests licensed for use in the United States:

	OraQuick Rapid HIV-1 and Advance HIV ½ Antibody Tests, manufactured by OraSure Technologies, Inc.
	Reveal G2 HIV-Antibody Tests, manufactured by MedMira, Inc.
	Multispot, manufactured by Bio-Rad Laboratories
	Uni-Gold Recombigen, manufactured by Trinity Biotech

The availability of these tests may differ from one place to another. These rapid HIV blood tests are considered to be just as accurate as the EIA. As is true for all screening tests (including the EIA), a positive test result must be confirmed with an additional specific test before a diagnosis of infection can be given.

What about home test kits?

The Food and Drug Administration (FDA) has not approved home-use HIV test kits, which allow consumers to interpret their own HIV test results in a few minutes. The Federal Trade Commission has warned that these home-use HIV test kits, many of which are available on the Internet, supply inaccurate results.

Currently only the Home Access test is approved by the Food and Drug Administration. The Home Access test kit can be found at most drug stores. The testing procedure involves pricking your finger, placing drops of blood on a specially treated card, and then mailing the card in for testing at a licensed laboratory. Customers are given an identification number to use when phoning for the test results. Callers may speak to a counselor before taking the test, while waiting for the test result, and when getting the result.

Getting Tested

Am I at risk?

Evidence suggests that HIV, the virus that causes AIDS, has been in the United States at least since 1978. The following are known risk factors for HIV infection. If you answer yes to any of these questions, you should definitely seek counseling and testing. You may be at increased risk of infection if any of the following apply to you since 1978.

	Have you injected drugs or steroids or shared equipment (such as needles, syringes, cotton, water) with others?
	Have you had unprotected vaginal, anal, or oral sex with men who have sex with men, multiple partners, or anonymous partners?
	Have you exchanged sex for drugs or money?
	Have you been diagnosed with or treated for hepatitis, tuberculosis (TB), or a sexually transmitted disease (STD), like syphilis?
	Have you received a blood transfusion or clotting factor between 1978 and 1985?
	Have you had unprotected sex with someone who would answer yes to any of the above questions?

If you have had sex with someone whose history of risk-taking behavior is unknown to you or if you or they may have had many sex partners, then you have increased the chances that you might be HIV infected.

If you plan to become pregnant, counseling and testing is even more important. If a woman is infected with HIV, medical therapies are available to lower the chance of passing HIV to the infant before, during, or after birth.

How do I know if I am infected?

The HIV-antibody test is the only way to tell if you are infected. You cannot tell by looking at someone if he or she carries HIV. Someone can look and feel perfectly healthy and still be infected. In fact, an estimated one-third of those who are HIV positive do not know it. Neither do their sex partners.

When HIV enters the bloodstream, it begins to attack certain white blood cells called T4 lymphocyte cells (helper cells). The immune system then produces antibodies to fight off the infection. Therefore, the presence of antibodies to HIV result from HIV infection. Testing can tell you whether or not you have developed antibodies to HIV.

If I think I have been exposed to HIV, how soon can I get tested?

To find out when you should be tested, discuss it with your testing site staff or personal physician. The tests commonly used to detect HIV infection actually look for antibodies produced by your body to fight HIV. Most people will develop detectable antibodies within 3 months after infection, the average being 20 days. In rare cases, it can take 6-12 months. During the time between exposure and the test, it is important to avoid any behavior that might result in exposure to blood, semen, or vaginal secretions.

Where can I get tested for HIV infection?

Many places offer HIV testing including local health departments, private doctors' offices, hospitals, and sites specifically set up to provide HIV testing. It is important to get tested at a place that also provides counseling about HIV and AIDS. Counselors can answer any questions you might have about risky behavior and ways you can protect yourself and others in the future. In addition, counselors can help you understand the meaning of the test results and tell you about AIDS-related resources in your area.

CDC-INFO (formerly the CDC National AIDS Hotline) can answer questions about testing and can refer you to testing sites in your area. You can also search this Website for a list of sites in your area. You may call CDC-INFO for assistance in English or in Spanish 24 hours a day, 365 days a year at:

1-800-CDC-INFO (1-800-232-4636)
TTY: 1-888-232-6348
In English, en Espanol
24 Hours/Day

To learn more about HIV testing, visit:

National HIV Testing Resources
This website offers information on testing and answers common questions regarding HIV testing. Please visit the HIV testing resources at: http://www.hivtest.org/.

The Body: HIV Testing
This website has a number of resources about testing methods, testing sites, testing guidelines, and up to date testing information. Also available are AIDS hotlines, Safe sex/prevention information, and what to do if you learn you are HIV positive. Please visit The Body at: http://www.thebody.com/testing.html.

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