What is Western Blot - HIV?
The Western blot and ELISA tests are two blood antibody tests that may be used to detect HIV.
In the past, the Western blot test was used to confirm the results of an ELISA test.
However, advances in technology mean that other methods are now commonly used. Since 2014, the Centers for Disease Control and Prevention (CDC) have recommended discontinuing the Western blot test.
Now, most laboratories use an immunoassay for the HIVp24 antigen and antibodies to HIV-1 and 2, followed by a confirmatory immunoassay to distinguish between HIV-1 and HIV-2.
Testing and diagnosis are an important part of staying healthy with HIV. With early diagnosis, early treatment is possible. Testing is the first step in accessing effective ways of managing the condition. It is the key to bothTrusted Source treatment and prevention.
Current treatment can reduce the viral load to undetectable levels. While levels are this low, the body can remain healthy, the individual can expect a normal lifespanTrusted Source, and the virus cannot be transmitted.
Explaining the tests
Laboratory blood tests can be used to diagnose HIV by detecting certain antibodies or proteins produced by the immune system in response to the virus.
The ELISA test also called the EIA for enzyme immunoassay, is used to detect the HIV antibody. It checks for certain proteins that the body makes in response to HIV.
The blood sample will be added to a cassette that contains the viral protein, called an antigen.
If the blood contains antibodies to HIV, it will bind with the antigen and cause the cassette’s contents to change color. This very sensitive test was the first one widely used to check for HIV.
The Western blot test was previously used to confirm the result of the ELISA, but it is no longer recommended, as other tests are now more reliable and enable a faster diagnosis.
In the Western blot test, the blood is taken in the same way, but the sample is separated with an electrical current and transferred onto a piece of blotting paper. Here, an enzyme is added to cause color changes that signal the presence of HIV antibodies.
Who has the tests?
Most adults will undergo screening at some time. It is a routine procedure during pregnancy.
However, the Western blot and ELISA tests are only recommended if a person may have been exposed to HIV.
People with a high risk of exposure include:
- those who have sex without using a condom, especially with someone who has HIV
- those who share needles
- people who had blood transfusions or injections prior to 1985
- those with other sexually transmitted diseases (STDs)
Some people choose to get tested for HIV fairly regularly, for example, if they have a new sexual partner or work in healthcare situations.
There is no special preparation for the ELISA test. It is a simple blood test.
Anyone undergoing HIV testing may want to tell the laboratory technician if they have a fear of needles or blood draws.
Additionally, some people may find it helpful to seek support from a relative or friend during HIV testing.