An estimated 1.2 million people in the United States are living with HIV, including 156,300 people who do not know they are infected. Each year, nearly 45,000 people are diagnosed with HIV, and 30% of new HIV infections are transmitted by people who are living with undiagnosed HIV. For those who are living with undiagnosed HIV, testing is the first step in maintaining a healthy life and reducing the spread of HIV.
CDC’s Revised Recommendations for HIV Testing of Adults, Adolescents, and Pregnant Women in Health-Care Settings advises routine HIV screening of adults, adolescents, and pregnant women in health care settings in the United States. The recommendations also call for reducing barriers to HIV testing. In April 2013, the U.S. Preventive Services Task Force (USPSTF) issued similar recommendations.
CDC recommends that everyone between the ages of 13 and 64 get tested for HIV at least once as part of routine health care. A general rule for those with risk factors is to get tested annually. Additionally, sexually active gay and bisexual men may benefit from getting an HIV test more often, perhaps every 3 to 6 months.
Data from a clinical trial sponsored by the National Institutes of Health indicate there is a clear personal health advantage to being diagnosed and starting therapy in the early course of HIV infection. This information further highlights the importance of routine HIV testing and its potential impact on better health outcomes. See Starting Antiretroviral Treatment Early Improves Outcomes for HIV-Infected Individuals for more information.
Importance of HIV Testing for Prevention and Treatment of HIV Infection
People with HIV who know they are infected can get HIV treatment (antiretroviral therapy, or ART) that can keep them healthy for many years. Studies indicate that all people living with HIV, including those with early infection, benefit from ART. Treatment with antiretroviral medications lowers the level of HIV in the blood (viral load), reduces HIV-related illness, and reduces the spread of HIV to others. Taking ART the right way every day can reduce an HIV-positive person’s chance of transmitting HIV by as much as 96%.
People living with HIV who know they are infected can also make other decisions that lower their risk of transmitting HIV to a partner. Studies have shown that many people with HIV who know they are infected avoid behaviors that might spread the infection to others with whom they have sex or share needles.
People who get tested and learn they are HIV-negative can also make decisions about sex, drug use, and health care that can protect them from HIV. For example, taking HIV medications daily, called pre-exposure prophylaxis or PrEP, can prevent HIV infection in persons who are HIV-negative and at very high risk for HIV.
HIV Tests For Screening and Diagnosis
HIV tests are very accurate, but no test can detect the virus immediately after infection. How soon a test can detect infection depends upon different factors, including the type of test being used. There are three types of HIV diagnostic tests: antibody tests, combination or fourth-generation tests, and nucleic acid tests (NATs).
- Antibody tests detect the presence of antibodies, proteins that a person’s body makes against HIV, not HIV itself. Most HIV tests, including most rapid tests and home tests, are antibody tests. It can take 3 to 12 weeks for a person’s body to make enough antibodies for an antibody test to detect HIV infection. In general, antibody tests that use blood can detect HIV slightly sooner after infection than tests done with oral fluid.
- Combination or fourth-generation tests look for both HIV antibodies and antigens. Antigens are a part of the virus itself and are present during acute HIV infection. It can take 2 to 6 weeks for a person’s body to make enough antigens and antibodies for a combination test to detect HIV. Combination tests are now recommended for testing done in labs and are becoming more common in the United States. There is also a rapid combination test available.
- NATs detect HIV the fastest by looking for HIV in the blood. It can take 7 to 28 days for NATs to detect HIV. This test is very expensive and is not routinely used for HIV screening unless the person recently had a high-risk exposure or a possible exposure with early symptoms of HIV infection.
An initial HIV test will either be an antibody test or combination test. It may involve obtaining blood or oral fluid for a rapid test or sending blood or oral fluid to a laboratory. If the initial HIV test is a rapid test and it is positive, the individual will be directed to get follow-up testing. If the initial HIV test is a laboratory test and is positive, the laboratory will usually conduct follow-up testing on the same blood specimen as the initial test. Although HIV tests are generally very accurate, follow-up testing allows the health care provider to be sure the diagnosis is right.
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- Page last reviewed: June 20, 2016
- Page last updated: June 20, 2016
- Content source: Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, Sexual Transmitted Diseases and Tuberculosis Prevention, Centers for Disease Control and Prevention