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negative antibody tests but alarming WB
Sep 30, 2008

Dear Dr. Bob

I've written to you a couple of times about my syndroms. To cut the story short I have had (and still have)almost all retrovirus infection syndromes. Recently i befriended a guy who has quite same story as mine sex with sex worker in condom but extnsive expouser to vaginal fluids. In his case it p happend 11 months ago my was 5 months we both tested negative with combo duo till now. Anyways he took western blott in 9 month and the result was sgp120 (+-)and sgp105 byy(+-) after 2 months his WB is p17 +- p24 - p31 +- gp41 +- sgp120+ sgp 105 - gp 36 -

he tests negative with combo duo I know he has some liver problems

does this look like he is going to be positive, perhaps this new strain undetectable by elisa ? or worse maybe it is new virus like HIV but yet to be discovered?

what is your opinion? Does he have it or something alike?

i am feeling so so (minor sore throats, indigestions etc.) My last negative HIV test was over 4 months post expousure? most of the time but what worries me the most is that my family gets sick more often recently :(

Response from Dr. Frascino

Hello,

Your friend's story is yet another example of why Western Blot tests should never ever be run without first obtaining a positive ELISA test. The Western Blot test (WB) is used only for confirmation of a positive ELISA (or EIA or rapid test). (See below.) Your friend's WB result is indeterminate and should never have been ordered, as your buddy is definitively HIV negative, just like you.

New strain undetectable by ELISA? No, of course not! This is merely yet another case of a test being run and interpreted inappropriately.

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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