An estimated 1.1 million people in the United States are living with HIV, including 166,000 people who do not know they are infected. In 2015, nearly 40,000 people were diagnosed with HIV. Thirty percent 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.
CDC. Monitoring selected national HIV prevention and care objectives by using HIV surveillance data—United States and 6 dependent areas—2013. HIV Surveillance Supplemental Report 2015;20(2). Accessed May 6, 2016.
CDC. Diagnoses of HIV infection in the United States and dependent areas, 2014. HIV Surveillance Report 2015;26. Accessed May 6, 2016.
CDC. HIV infection, risk, prevention, and testing behaviors among men who have sex with men—national HIV behavioral surveillance, 20 U.S. cities, 2014. HIV Surveillance Special Report 2016:15. Accessed May 6, 2016.
CDC. HIV infection, risk, prevention, and testing behaviors among persons who inject drugs—national HIV behavioral surveillance: injection drug use, 20 U.S. cities, 2012. HIV Surveillance Special Report 2015. Revised edition. Accessed May 6, 2016.
CDC. Prevalence of diagnosed and undiagnosed HIV Infection — United States, 2008–2012. MMWR 2015;64:657-662.
CDC. CDC-funded HIV testing: United, States, Puerto Rico and the U.S. Virgin Islands, 2014. Published April 2016. Accessed May 6, 2016.
CDC and Association of Public Health Laboratories. Laboratory testing for the diagnoses of HIV infection: updated recommendations. Published June 2014. Accessed May 6, 2016.
Cohen MS, Chen YQ, McCauley M, et al. Prevention of HIV-1 infection with early antiretroviral therapy. N Engl J Med 2011;365:493-505.
Kitahata MM, Gange SJ, Abraham AG, et al. North American AIDS Cohort Collaboration on Research and Design Investigators. Effect of early versus deferred antiretroviral therapy for HIV on survival. N Engl J Med 2009;360:1815-26.
Luo W, Masciotra S, Delaney KP, et al. Comparison of HIV oral fluid and plasma antibody results during early infection in a longitudinal Nigerian cohort. J Clin Virol 2013;58(suppl 1): e113-8. PubMed abstract.
Masciotra S, Luo W, Youngpairoj AS, et al. Performance of the Alere Determine HIV-1/2 Ag/Ab Combo Rapid Test with specimens from HIV-1 seroconverters from the US and HIV-2 infected individuals from Ivory Coast. J Clin Virol 2013; 58 (suppl 1): e54-8. PubMed abstract.
Quinn TC, Wawer MJ, Sewankambo N, et al. Viral load and heterosexual transmission of human immunodeficiency virus type 1. N Eng J Med 2000;342:921-9.
Skarbinski J, Rosenberg E, Paz-Bailey G, et al. Human immunodeficiency virus transmission at each step of the care continuum in the United States. JAMA Intern Med 2015;175:588-96. PubMed abstract.
Smith MK, Rutstein SE, Powers KA, et al. The detection and management of early HIV infection: a clinical and public health emergency. J Acquir Immune Defic Syndr 2013; 63 (suppl 2):S187-99.
- Page last reviewed: May 18, 2017
- Page last updated: May 18, 2017
- 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