As the body fights a particular virus, it creates substances called antibodies to that virus. Tests for HIV usually measure the presence of HIV antibodies in blood, urine, or saliva, rather than testing for the presence of HIV itself (San Francisco AIDS Foundation [SFAF], 1998a).
Several different types of tests can be used to detect HIV. An Enzyme-Linked Immunosorbent Assay (ELISA) determines HIV antibodies' presence in blood or oral fluids. When people show HIV antibodies on two or more ELISA tests, they undergo an independent, highly specific supplemental test (most commonly, the Western Blot test) to confirm ELISA's results (Constantine, n.d.). Western Blot is a highly specific supplemental test that detects the presence of HIV antibodies in the blood. The Western Blot test is less sensitive than the ELISA test, but it hardly ever gives a false positive result; therefore, it is used for confirming the ELISA test. Rapid serum HIV antibody tests, saliva- and urine-based antibody tests, and home HIV antibody testing kits also have been approved by the Food and Drug Administration (FDA) and are commercially available (Constantine, n.d.). The rapid HIV tests can be administered outside of a traditional laboratory setting and processed in as little as 20 minutes (CDC, 2003b, 2006). HIV RNA tests are being used in research and healthcare settings to diagnose HIV infection very early after exposure, before antibodies are even formed (Constantine, n.d.). These tests look for bits of HIV RNA in the blood.
Most HIV testing is combined with HIV risk-reduction counseling and referral for HIV/AIDS treatment (if the person does have HIV). This combination of services is known as Counseling, Testing, and Referral (CTR) or Voluntary Counseling and Testing (VCT). VCT offers a number of benefits. When HIV-infected people learn of their positive serostatus, they may be able to obtain treatment that can reduce their symptoms and increase their life spans. HIV testing and accompanying counseling also can help people with HIV to initiate behavioral changes that will reduce the likelihood of their being infected with a different strain of HIV or of passing HIV to others. HIV-negative (HIV- or seronegative for HIV) people also can benefit from testing and accompanying counseling, as it may provide them with the knowledge and motivation that they need to take further steps to protect themselves from HIV. In addition, the data that researchers and healthcare workers obtain from analyzing HIV test results help them to learn more about HIV epidemiology and mechanisms of transmission (CDC, 2001, 2006; Family Health International [FHI], 2003; Roland, Fine, & Volberding, 1998).
Discussion question: In the United States, many HIV-infected individuals do not get tested until late in their infections. Why? What can be done to change this?
In the United States, many HIV-infected individuals do not get tested until late in their infections. As a result, they are already very sick when they first learn that they have HIV. For example, of the 104,780 people who tested positive for HIV between 1994 and 1999, 41% developed AIDS within 1 year (CDC, 2003a). Additionally, people who are tested do not necessarily return to learn their test results. For example, in 2000, of an estimated 2 million CDC-funded HIV tests, approximately 18,000 tests represented new HIV diagnoses. During 2000, of persons with positive tests for HIV, 31% did not return for their test results (CDC, 2003a).
An emphasis on expanding access to testing and on providing prevention and care services for people infected with HIV can reduce new infections and lead to reductions in HIV-associated morbidity and mortality (CDC, 2003a). Strategies to increase access to HIV testing include making HIV testing a routine part of medical care and implementing new models for diagnosing HIV infections outside of medical settings (CDC, 2003b).
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