posted
What is the deal with the false positive due to HSV,EBV or HCV infections? I understand why syphilis could cause a false positive.
Just wondering if further testing should be done even though results are CDC/IgeneX IgM pos and IgeneX IgG pos.
hoot
Posts: 236 | From Illinois | Registered: Feb 2009
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disturbedme
Frequent Contributor (1K+ posts)
Member # 12346
posted
No, it really depends on the bands you get.... some bands are lyme-specific so none of these other viruses could cause those to show up and thus get a 'false positive'. And Syphilis can NOT cause a false positive (*maybe* on band 41 only), especially if you are speaking of the Western Blot (and not the ELISA).
-------------------- One can never consent to creep when one feels an impulse to soar. ~ Helen Keller
My Lyme Story Posts: 2965 | From Land of Confusion (bitten in KS, moved to PA, now living in MD) | Registered: Jun 2007
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quote:Originally posted by disturbedme: No, it really depends on the bands you get.... some bands are lyme-specific so none of these other viruses could cause those to show up and thus get a 'false positive'. And Syphilis can NOT cause a false positive (*maybe* on band 41 only), especially if you are speaking of the Western Blot (and not the ELISA).
Here is a better interpretation to help you calm your nerves. The below is taken from the Igenx Website:
The Lyme IgG or IgM 30-31kDA confirmation test is a qualitative immunoblot assay that determines whether 30 and/or 31kDA bands present on a Lyme IgG or IgM western blot are due to B. burgdorferi specific antibodies or not. B. burgdorferi specific epitope(s) - 30 and/or 31kDA, are denatured and separated by SDS polyacrylamide gel electrophoresis, blotted onto nitrocellulose membranes and cut into strips for the use of Lyme 30-31kDA Western Blot Confirmation Test. It is known that Western blots, especially IgM, can give false positive results with some viruses. This test would be very useful to rule out false positives when 30 and/or 31kDa bands are present on the Western blots.
The IGeneX Lyme Western blots determine whether a patient was exposed to B. burgdorferi or not. The IgG or IgM Western blot has an overall specificity of >96%; and the combined IgG and IgM Western Blots have a sensitivity of 92%. This is based on a study performed on 142 well characterized serum samples. The Lyme Western blot strips have bound B. burgdorferi proteins that are separated by molecular weight. Therefore, non-specific proteins present in the B. burgdorferi lysate co-migrate with B. burgdorferi specific proteins. The non-specific co-migrating proteins can give false positive results as has been demonstrated by us and others. When we tested Lyme Western blots against a panel of 94 sera from patients with viral infections (confirmed by presence of antibodies to viruses), the assay specificity for Lyme Western blot IgG dropped to 90% and IgM to 81%. The Lyme IgG Western blot bands 30-31kDa confirmation test improved the specificity for IgG to >97% and for IgM >98% (See table below). In addition when a panel of very well characterized 30 sera from patients with neuroborreliosis, that were part of an NIH study, (provided by Dr. Fallon, Columbia University) were tested, the assay sensitivity was >97% (29/30 were positive). Based on this data, we recommend that further testing is not necessary if in addition to 30 and/or 31kDa bands, two of the following bands (23-25, 34, 39,41 and 83-93 kDa), are present on the Western blot. Otherwise, the 30-31kDA confirmation test should be used to confirm whether 30-31kDa bands present on the Lyme Western blots are due to B. burgdorferi specific antibodies or not. If the 30-31kDa confirmation test is negative, we recommend that patient's sera be tested for viral antibodies.
Posts: 101 | From Living in the Now | Registered: Mar 2009
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