HIV Testing Basics
- Should I get tested?
- How long after a possible exposure should I wait to get tested for HIV?
- How do HIV tests work?
- What are the different HIV screening tests available in the United States?
- If I test HIV negative, does that mean that my partner is HIV negative also?
- What if I test positive for HIV?
- If I'm HIV positive, where can I get information about treatment?
- Where can I get tested for HIV infection?
- Why is it recommended for pregnant women to be tested for HIV?
Should I get tested?
The following are behaviors that increase your chances of getting HIV. If you answer yes to any of them, you should definitely get an HIV test. If you continue with any of these behaviors, you should be tested every year. Talk to a health care provider about an HIV testing schedule that is right for you.
- Have you injected drugs or steroids or shared equipment (such as needles, syringes, works) 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 had unprotected sex with someone who could answer yes to any of the above questions?
If you have had sex with someone whose history of sex partners and/or drug use is unknown to you or if you or your partner has had many sex partners, then you have more of a chance of being infected with HIV. Both you and your new partner should get tested for HIV, and learn the results, before having sex for the first time.
For women who plan to become pregnant, testing is even more important. If a woman is infected with HIV, medical care and certain drugs given during pregnancy can lower the chance of passing HIV to her baby. All women who are pregnant should be tested during each pregnancy.
How long after a possible exposure should I wait to get tested for HIV?
Most HIV tests are antibody tests that measure the antibodies your body makes against HIV. It can take some time for the immune system to produce enough antibodies for the antibody test to detect, and this time period can vary from person to person. This time period is commonly referred to as the “window period.” Most people will develop detectable antibodies within 2 to 8 weeks (the average is 25 days). Even so, there is a chance that some individuals will take longer to develop detectable antibodies. Therefore, if the initial negative HIV test was conducted within the first 3 months after possible exposure, repeat testing should be considered >3 months after the exposure occurred to account for the possibility of a false-negative result. Ninety-seven percent of persons will develop antibodies in the first 3 months following the time of their infection. In very rare cases, it can take up to 6 months to develop antibodies to HIV.
Another type of test is an RNA test, which detects the HIV virus directly. The time between HIV infection and RNA detection is 9–11 days. These tests, which are more costly and used less often than antibody tests, are used in some parts of the United States.
For information on HIV testing, you can talk to your health care provider or you can find the location of the HIV testing site nearest to you by visiting the National HIV Testing Resources Web site (http://www.hivtest.org/) or call CDC-INFO 24 Hours/Day at 1-800-CDC-INFO (232-4636), 1-888-232-6348 (TTY), in English, en Español. Both of these resources are confidential.
How do HIV tests work?
Once HIV enters the body, the immune system starts to produce antibodies – (chemicals that are part of the immune system that recognize invaders like bacteria and viruses and mobilize the body's attempt to fight infection). In the case of HIV, these antibodies cannot fight off the infection, but their presence is used to tell whether a person has HIV in his or her body. In other words, most HIV tests look for the HIV antibodies rather than looking for HIV itself. There are tests that look for HIV's genetic material directly, but these are not in widespread use.
The most common HIV tests use blood to detect HIV infection. Tests using saliva or urine are also available. Some tests take a few days for results, but rapid HIV tests can give results in about 20 minutes. All positive HIV tests must be followed up by another test to confirm the positive result. Results of this confirmatory test can take a few days to a few weeks.
What are the different HIV screening tests available in the United States?
In most cases the EIA (enzyme immunoassay), used on blood drawn from a vein, is the most common screening test used to look for antibodies to HIV. A positive (reactive) EIA must be used with a follow-up (confirmatory) test such as the Western blot to make a positive diagnosis. There are EIA tests that use other body fluids to look for antibodies to HIV. These include:
- Oral Fluid Tests – use oral fluid (not saliva) that is collected from the mouth using a special collection device. This is an EIA antibody test similar to the standard blood EIA test. A follow-up confirmatory Western blot uses the same oral fluid sample.
- Urine Tests – use urine instead of blood. The sensitivity and specificity (accuracy) are somewhat less than that of the blood and oral fluid tests. This is also an EIA antibody test similar to blood EIA tests and requires a follow-up confirmatory Western blot using the same urine sample.
A rapid test is a screening test that produces very quick results, in approximately 20 minutes. Rapid tests use blood from a vein or from a finger stick, or oral fluid, to look for the presence of antibodies to HIV. As is true for all screening tests, a reactive rapid HIV test result must be confirmed with a follow-up confirmatory test before a final diagnosis of infection can be made. These tests have similar accuracy rates as traditional EIA screening tests.
Home Testing Kits
Consumer-controlled test kits (popularly known as "home testing kits") were first licensed in 1997. Although home HIV tests are sometimes advertised through the Internet, currently only the Home Access HIV-1 Test System (http://www.fda.gov/
ApprovalsPMAs/ucm091475.htm) is approved by the Food and Drug Administration. (The accuracy of other home test kits cannot be verified.) The Home Access HIV-1 Test System can be found at most local drug stores. It is not a true home test, but a home collection kit. The testing procedure involves pricking a finger with a special device, placing drops of blood on a specially treated card, and then mailing the card in to be tested at a licensed laboratory. Customers are given an identification number to use when phoning in for the results. Callers may speak to a counselor before taking the test, while waiting for the test result, and when the results are given. All individuals receiving a positive test result are provided referrals for a follow-up confirmatory test, as well as information and resources on treatment and support services.
RNA tests look for genetic material of the virus and can be used in screening the blood supply and for detection of rare very early infection cases when antibody tests are unable to detect antibodies to HIV.
If I test HIV negative, does that mean that my partner is HIV negative also?
No. Your HIV test result reveals only your HIV status. Your negative test result does not indicate whether or not your partner has HIV. HIV is not necessarily transmitted every time you have sex. Therefore, your taking an HIV test should not be seen as a method to find out if your partner is infected.
Ask your partner if he or she has been tested for HIV and what risk behaviors he or she has engaged in, both currently and in the past. Think about getting tested together.
It is important to take steps to reduce your risk of getting HIV. Not having (abstaining from) sex is the most effective way to avoid HIV. If you choose to be sexually active, having sex with one person who only has sex with you and who is uninfected is also effective. If you are not sure that both you and your partner are HIV negative, use a latex condom to help protect both you and your partner from HIV and other STDs. Studies have shown that latex condoms are very effective, though not 100%, in preventing HIV transmission when used correctly and consistently. If either partner is allergic to latex, plastic (polyurethane) condoms for either the male or female can be used.
What if I test positive for HIV?
If you test positive for HIV, the sooner you take steps to protect your health, the better. Early medical treatment and a healthy lifestyle can help you stay well. Prompt medical care may delay the onset of AIDS and prevent some life-threatening conditions. There are a number of important steps you can take immediately to protect your health:
- See a licensed health care provider, even if you do not feel sick. Try to find a health care provider who has experience treating HIV. There are now many medications to treat HIV infection and help you maintain your health. It is never too early to start thinking about treatment possibilities.
- Have a TB (tuberculosis) test. You may be infected with TB and not know it. Undetected TB can cause serious illness, but it can be successfully treated if caught early.
- Smoking cigarettes, drinking too much alcohol, or using illegal drugs (such as methamphetamines) can weaken your immune system. There are programs available that can help you stop or reduce your use of these substances.
- Get screened for other sexually transmitted diseases (STDs). Undetected STDs can cause serious health problems. It is also important to practice safe-sex behaviors so you can avoid getting STDs.
There is much you can do to stay healthy. Learn all that you can about maintaining good health.
Not having (abstaining from) sex is the most effective way to avoid transmitting HIV to others. If you choose to have sex, use a latex condom to help protect your partner from HIV and other STDs. Studies have shown that latex condoms are very effective, though not 100%, in preventing HIV transmission when used correctly and consistently. If either partner is allergic to latex, plastic (polyurethane) condoms for either the male or female can be used.
If I'm HIV positive, where can I get information about treatment?
CDC recommends that you be in the care of a licensed health care provider, preferably one with experience treating people living with HIV. Your health care provider can assist you with treatment information and guidance.
Detailed information on specific treatments is available from the Department of Health and Human Services' AIDSinfo (http://www.aidsinfo.nih.gov/). Information on enrolling in clinical trials is also available at AIDSinfo. You may contact AIDSinfo by phone at 1-800-448-0440 (English and Spanish) or 1-888-480-3739 (TTY).
Where can I get tested for HIV infection?
Many places provide testing for HIV infection. Common testing locations include local health departments, clinics, offices of private doctors, hospitals, and other sites set up specifically to provide HIV testing. You can also ask your health care provider about getting tested, or, For information on HIV testing, you can talk to your health care provider or you can find the location of the HIV testing site nearest to you by visiting the National HIV Testing Resources Web site (http://www.hivtest.org/)or call CDC-INFO 24 Hours/Day at 1-800-CDC-INFO (232-4636), 1-888-232-6348 (TTY), in English, en Español. Both of these resources are confidential.
Between the time of a possible exposure and the receipt of test results, individuals should consider abstaining from sexual contact with others or use condoms and/or dental dams during all sexual encounters.
If you have questions about HIV or AIDS, it is important to seek testing at a place that also provides counseling about HIV prevention and AIDS. Counselors can answer any questions you might have about risky behaviors and ways you can protect yourself and others in the future. In addition, they can help you understand the meaning of the test results and describe what HIV/AIDS-related resources are available in the local area. If you would like more information or have personal concerns, call CDC-INFO 24 Hours/Day at 1-800-CDC-INFO (232-4636), 1-888-232-6348 (TTY), in English, en Español.
Why is it recommended for pregnant women to be tested for HIV?
HIV testing during pregnancy is important because antiviral therapy can improve the mother's health and greatly lower the chance that an HIV-infected pregnant woman will pass HIV to her infant before, during, or after birth. The treatment is most effective for babies when started as early as possible during pregnancy. However, there are still great health benefits to beginning treatment even during labor or shortly after the baby is born.
CDC recommends HIV screening for all pregnant women because risk-based testing (when the health care provider offers an HIV test based on the provider's assessment of the pregnant woman's risk) misses many women who are infected with HIV. CDC does recommend providing information on HIV (either orally or by pamphlet) and, for women with risk factors, referrals to prevention counseling.
HIV testing provides an opportunity for infected women to find out that they are infected and to gain access to medical treatment that may help improve their own health. It also allows them to make informed choices that can prevent transmission to their infant. For some uninfected women with risks for HIV, the prenatal care period could be an ideal opportunity for HIV prevention and subsequent behavior change to reduce risk for acquiring HIV infection.
Centers for Disease Control
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