According to the National Institute of Allergy and Infectious Diseases, 21 percent of Americans infected with HIV are unaware that they have the disease. Only an HIV test can definitively determine whether someone is infected with the virus and likely to develop AIDS.
Types
An ELISA test--an enzyme-linked immunosorbent assay--is a biochemical test that looks for antibodies against HIV in a sample of blood. A positive result on an ELISA test generally results in a repeat test, which is then followed up with a Western blot test, which looks for viral proteins in the blood sample. It takes about two weeks for the results of these tests to come back.
Rapid tests take about 20 minutes. They involve a test strip lined with antigens to HIV, which bind to any antibodies present in the sample and create a line or dot on the strip to indicate a positive result. A rapid test can be performed on a swab of oral fluids collected from the gums or on a blood sample. A positive rapid test result is typically referred for further testing.
An RNA test is available at some clinics. It can detect the genetic material of the virus itself. An RNA test is costlier than other types and often difficult to find.
The FDA-approved Home Access HIV-1 test is a mail-in test. An individual takes a sample of oral fluids swabbed from the gums and sends it to a lab for confidential testing.
Timing
HIV is not immediately detectable in the body right after infection since the body needs time to build up antibodies against it. Ninety-seven percent of infected individuals develop antibodies by three months after infection, according to the Centers for Disease Control (CDC), but some people take as long as six months. Anyone with a negative test result three months or less after suspected exposure should get retested after six months to confirm the negative result. Infants born to infected mothers should be tested between 3 months and 15 months of age, since before this point a baby will carry antibodies of the mother and test positive even if he doesn't have the disease. An RNA test can provide an accurate diagnosis for anyone nine to 11 days after exposure to HIV, as the test looks for viral RNA in the blood sample, not antibodies produced by the host.
Who Should Be Tested
The CDC recommends testing every year for sexually active adults not in a long-term monogamous relationship. Anyone who suspects they may have been exposed to HIV should also undergo testing. All pregnant women should be tested for HIV, since treatment during pregnancy and birth can significantly reduce the chances of passing the infection to the baby.
Procedure
For a blood test to look for HIV antibodies or proteins, blood is drawn from a vein in the arm or back of the hand and sent to a lab. For HIV testing of infants, a small puncture is made in the skin and blood is collected with a thin tube, instead of with a traditional needle and syringe. A home test comes with a swab to collect a sample of saliva from the gums, which is then sealed in a provided container and shipped to the lab for analysis. Results from a home test are sent through the mail.
Results
An individual without HIV will receive a negative test result. However, false negatives are also possible, especially if the test is done too early. False positives can occur on an ELISA test, so it is always followed up with a Western blot test.
