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HIV Testing

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For more information, please visit gettested.cdc.gov

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Background

An estimated 1.1 million people in the United States are living with HIV, including about 162,500 people who are unaware of their status. Approximately 40% 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 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 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. For those with specific risk factors, CDCDC recommends getting tested at least once a yearC recommends getting tested once a year.

Data from a clinical trial sponsored by the National Institutes of Health shows a clear personal health advantage to being diagnosed with HIV early and starting therapy right away. This information further highlights the importance of routine HIV testing and its potential impact on better health outcomes.

hiv testing

Importance of HIV Testing for Prevention of HIV Infection

People with HIV who are aware of their status can get HIV treatment (antiretroviral therapy, or ART) and remain healthy for many years. Studies show that the sooner people start treatment after diagnosis, the more they benefit from ART. Treatment with ART lowers the level of HIV in the blood (viral load), reduces HIV-related illness, and lowers the risk of transmitting HIV to others. People living with HIV who take ART as prescribed and get and keep an undetectable viral load have effectively no risk of sexually transmitting HIV to an HIV-negative partner.

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 people at very high risk for HIV, taking daily HIV medicine called pre-exposure prophylaxis or PrEP can prevent HIV infection by more than 90%.

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: nucleic acid tests (NAT), antigen/antibody tests, and antibody tests.

  • NATs look for the actual virus in the blood. 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.
  • Antigen/antibody tests look for both HIV antibodies and antigens. Antigens are foreign substances that cause your immune system to activate. If you’re infected with HIV, an antigen called p24 is produced even before antibodies develop. Tests that detect both antigen and antibodies are recommended for testing done in labs and are now common in the United States. There is also a rapid antigen/antibody test available.
  • Antibody tests detect the presence of antibodies, proteins that a person’s body makes against HIV, not HIV itself. Most rapid tests and home tests are antibody tests.

An initial HIV test usually will either be an antigen/antibody test or an antibody test. If the initial HIV test is a rapid test and it is positive, the individual will be sent to a health care provider to get follow-up testing. If the initial HIV test is a laboratory test and it is positive, the laboratory will usually conduct follow-up testing on the same blood sample 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.

Resources for FDA-approved laboratory tests and home tests are available. Learn more about testing in nonclinical settings and testing in clinical settings.

Bibliography

CDC. Diagnoses of HIV infection in the United States and dependent areas, 2016. HIV Surveillance Report 2017;28. Accessed April 10, 2018.<

CDC. Monitoring selected national HIV prevention and care objectives by using HIV surveillance data—United States and 6 dependent areas, 2015. HIV Surveillance Supplemental Report 2017;22(2). Accessed September 6, 2017.

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 September 6, 2017.

CDC. HIV infection, risk, prevention, and testing behaviors among persons who inject drugs—national HIV behavioral surveillance: injection drug use, 20 U.S. cities, 2015. HIV Surveillance Special Report 2017;18. Revised edition. Accessed April 13, 2018.

CDC. HIV Infection, Risk, Prevention, and Testing Behaviors Among Heterosexuals at Increased Risk of HIV Infection—National HIV Behavioral Surveillance, 17 U.S. Cities. HIV Surveillance Special Report.2016;19. Accessed April 13, 2018.

CDC. CDC-funded HIV testing: United, States, Puerto Rico and the U.S. Virgin Islands, 2015. Published April 2017.

CDC. Human Immunodeficiency Virus Testing and Diagnosis Delays—United States, 2017. MMWR 2017; 66(47);1300–1306.

CDC. Recommendations for HIV screening of gay, bisexual, and other men who have sex with men—United States, 2017. MMWR 2017;66(31);830-2.

CDC. Prevalence of diagnosed and undiagnosed HIV infection—United States, 2008–2012. MMWR 2015;64:657-662.

CDC. Revised recommendations for HV testing of adults, adolescents, and pregnant women in health-care settings. MMWR 2006;55:1-17.

CDC and Association of Public Health Laboratories. Laboratory testing for the diagnoses of HIV infection: updated recommendations. Published June 2014. Accessed September 6, 2017.

Delaney KP, Hanson DL, Masciotra S, et al. Time until emergence of HIV test reactivity following infection with HIV-1: Implications for interpreting test results and retesting after exposure. Clin Infect Dis 2017;64(1):53-9.

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.

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