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Testing and Diagnosis

Routine HIV Testing

photo of a woman giving blood
HIV testing involves taking a blood sample. Credit: NIAID.

Of the estimated 1.1 million Americans currently living with HIV, 21 percent do not know they are infected. People who have been infected recently with HIV often have few to no symptoms yet are extremely infectious and may unknowingly transmit the virus to others. Therefore, the Centers for Disease Control and Prevention (CDC) recommends HIV testing for adults, adolescents, and pregnant women during routine medical care.1 Regular HIV screenings allow healthcare providers to identify people who are not aware that they are infected with HIV, so that they can be counseled on the need to avoid high-risk behaviors, instructed on safe-sex practices, and given information about starting antiretroviral therapy. HIV testing can also be performed anonymously if a person is concerned about confidentiality.

Types of HIV Tests

Healthcare providers can test a sample of blood to see if it contains human antibodies (disease-fighting proteins) specific to HIV. The two key types of HIV antibody tests are the enzyme-linked immunosorbent assay (ELISA) and the Western blot.

However, these antibody tests may not detect HIV antibodies in someone who has been recently infected with HIV (within 1 to 3 months of infection). In these situations, healthcare providers can test the blood for the presence of HIV genetic material. This test is extremely critical for identifying recently infected people who are at risk for unknowingly infecting others with HIV.

HIV Testing in Infants

CDC recommends that all pregnant women get tested for HIV before and/or during delivery. Knowing the HIV status of the mother allows physicians to prevent mother-to-child HIV transmission by providing antiretroviral treatment to both mothers infected with HIV and their newborn infants. However, it is difficult to determine if a baby born to a mother infected with HIV is actually infected because babies carry their mothers’ HIV antibodies for several months. Today, healthcare providers can conduct an HIV test for infants between ages 3 months and 15 months. Researchers are now evaluating several blood tests to determine which ones are suitable for testing babies younger than 3 months.

Reference

1Revised Recommendations for HIV Testing of Adults, Adolescents, and Pregnant Women in Health-Care Settings, September 2006.

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Last Updated April 28, 2009

Last Reviewed April 28, 2009