Category: Lyme testing (blood, spinal fluid...)
Is it possible to have negative western blot test and have Lyme disease?
Yes, it is possible to have a negative Western blot and have Lyme Disease. The Western Blot is a test that tells you what antibodies exist in the blood serum against proteins of a certain molecular weight. A Western blot report will usually tell you which bands or antibodies were identified. The Western blot test is a better test than the ELISA because it is more specific. For example, at a good lab, a positive IgG Western blot is 100% specific for exposure to the agent of Lyme Disease. A positive ELISA howvever is much less specific, because it does not separate out the Lyme-specific bands from bands that arise from "cross-reactive" antibodies as one might see among patients with other diseases such as lupus or rheumatoid arthritis.
The IgM Western blot is well recognized as having insufficient sensitivity in early Lyme disease. The IgG Western blot may not become postive until 6 or more weeks later. So, the staging of the infection is important. In addition, if a person has received antibiotics, this may suppress or abrograte the immune response so that a person may test negative on the ELISA or Western blot even though a definite Lyme infection occurred. The FDA recommendation is that the diagnosis of Lyme Disease be made on clinical grounds rather than relying only on blood testing for the diagnosis.
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