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Dr Robert is an Hiv WesternBlot (ELISA versus WESTERN BLOT tests for diagnostic screening)
Sep 29, 2008

Dr Robert is an Hiv Western Blot alot better then reg HIv 1/2 Elisa. Yeah I had My Dr run them both tests and they are Negative. Thanks'

Response from Dr. Frascino

Hello,

Western Blot tests should only be run to confirm a repeatedly reactive (positive) ELISA (or EIA or rapid test). It should not be used as a diagnostic tests without a positive initial screening test, due to the possibility of false-positive or indeterminate Western Blot results. This has to do with the sensitivity and specificity of these two tests (see below). You can learn much more about HIV testing by reviewing the chapter "HIV Testing Basics" that can be easily accessed on The Body's homepage under the Quick Links heading. Check it out!

Dr. Bob

ELISA

The ELISA (also sometimes called EIA) is almost always the first screening tool; it is inexpensiveand very sensitive for detecting the presence of HIV antibodies. In most cases, a blood sample is tested, but other types of ELISAs that use saliva and urine have also been developed. The actual ELISA takes 3.5 to 4 hours, but most test sites send samples to outside labs, where they are tested in batches, so you may have to wait one to two weeks for results. Beyond the "window period," ELISA tests are very rarely "false negative." This means if you have a negative test result, and you were tested at least six months after the last potential exposure, you are really HIV negative. An ELISA test may rarely be "false positive." False positive ELISA results can occur if someone is tested right after events that temporarily stimulate the immune system, such as viral infections or immunizations. They could also occur because of lab error, or because of the test's very high sensitivity, discussed below. For these reasons, positive ELISA results must always be confirmed with a Western Blot or IFA (below), and at reputable test sites this is commonly done automatically -- meaning you don't have to have another blood sample drawn. A relatively new test, called a detuned ELISA, which has been used in research settings, will soon become more widely available to other test sites. The detuned test, which is used only after HIV antibodies are confirmed by a Western Blot test, can determine if the HIV infection is recent (within the last six months), which may be useful for deciding upon possible early treatmentoptions.

Western Blot (WB) Assay

The WB is a confirmatory test: it is only performed if the ELISA is positive. The WB can be positive, negative, or indeterminate. Indeterminate tests are neither positive nor negative. An indeterminate result usually means that a person has just begun to seroconvert at the time of their test. In the rare cases in which this occurs, the person will need to be retested, usually about one month later. False positive results are extremely rare with the WB, so it confirms (proves) that HIV antibodies are present.



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