HIV Testing (cont.)
What are Different Types of HIV Tests?
The two types of antibody tests most commonly used to detect HIV infection are the ELISA (enzyme-linked immunoassay) and Western blot tests. These tests are very accurate, but they are only able to detect HIV antibodies and not the HIV virus particle itself.
- A process is followed to determine if you are HIV positive.
- First, the ELISA test is performed.
- If the ELISA test is negative for the detection of HIV antibodies, the test is reported as negative.
- If the sample is repeatedly reactive or positive by ELISA, the results are then confirmed using the Western blot test.
- The Western blot test is more accurate, though it is also more expensive and takes longer to perform.
- As a combination, the ELISA and Western blot tests have a very high degree of accuracy when the sample is taken outside of the window period.
- If both the ELISA and Western blot tests are positive, you are presumed to be HIV positive.
You can also test yourself anonymously for HIV at home. Currently, only the "Home Access HIV-1 Test System" or the "Home Access Express HIV-1 Test System" home blood test is approved by the U.S. Food and Drug Administration. The test kit can be found at most drug stores at a cost of $45-$70.
- The testing procedure involves pricking your finger, placing drops of blood on a specially treated card, and then mailing the card in for testing at a licensed laboratory.
- The test uses traditional ELISA and Western blot procedures and has been shown to be as reliable as HIV tests used by doctors and hospitals.
- People who use this test are given an identification number to use when phoning for the test results in three business days.
- The company provides HIV counseling and medical referrals, and test results are available 24 hours a day, seven days a week.
- Several states have attempted to block the sale of Home Access HIV Test kits, citing their laws that mandate the reporting of names of HIV-infected people. But federal court rulings have upheld the FDA approval of the Home Access HIV Test kits over the more restrictive state laws.
Although the ELISA and Western blot are the most commonly used tests for HIV, other HIV tests can be performed with even higher accuracy and fewer uncertainties concerning the window period. These tests detect the actual HIV virus particles/nucleic acids, or viral load, as opposed to the HIV antibody.
- Although extremely sensitive (some viral load tests can detect a single virus particle in as many as 100,000 cells), they are labor-intensive and not recommended for routine HIV testing.
These tests must be ordered by a doctor and therefore cannot be performed anonymously. The viral load HIV tests are usually reserved to guide antiviral therapy for people known to be HIV infected, pregnant women, and infants born to mothers with HIV.
Leon Salem, MD, MS, FACEP