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OverviewLyme Antibody Serology Lyme IgG/IgM Antibody Serology The Lyme IgG/IgM Antibody Serology test is an enzyme linked immunoassay (ELISA) which indicates the presence of IgG and IgM antibodies to B. burgdorferi. The IgG antibody often persists long after symptoms have disappeared. The presence of antibody indicates exposure, not necessarily active disease. A positive or equivocal result must be confirmed by both IgG and IgM Western Blots. Lyme IgM Antibody Serology The Lyme IgM Antibody assay is another serologic test in ELISA format, and it detects the presence of IgM antibodies after exposure to an infected tick. IgM antibodies apppear early in response to infection, and this test may be positive two to six weeks following exposure. Because of the test's lack of specificity, a positive or equivocal result must be confirmed by an IgM Western Blot. Lyme Western Blot IgG Western Blot The IgG Western Blot is a sandwich-type immunoassay performed in a manner that allows the antibody response to be visualized. It is a qualitative test and is generally more sensitive and specific than the ELISA. IgM Western Blot This test is a very sensitive indicator of exposure to B. burgdorferi. It may be positive as early as one week after a tick bite, and will usually remain positive for six to eight weeks after initial exposure. A positive IgM result with clinical history can indicate early Lyme disease, or even persistent infection in otherwise serologically negative individuals. Antigen Detection Lyme Dot Blot Assay (LDA)* The LDA is an immunoassay for the direct detection of Lyme antigen in urine that reacts specifically to rabbit anti-B. burgdorferi antibodies. The rabbit antibodies are specifically targeted to the following B. burgdorferi antigens: 23kDA–25kDA (Osp C), 31 kDA (Osp A), 34 kDA (Osp B), 39kDA and/or 93kDA. If the Borrelia specific antigen(s) are present in the urine sample, a dot with a bluish-purple precipitate forms on the membrane. The limit of detection in urine spiked with sonicated B. burgdorferi is 12.5 ng/ml of urine. Reverse Western Blot (RWB) for Antigen* The RWB is an immunoassay for direct detection and identification of Lyme antigen in urine which specifically react with rabbit anti-B. burgdorferi antibodies. The rabbit antibodies are specifically targeted to the following B. burgdorferi antigens: 18kDA, 23kDA–25kDA (Osp C), 28kDa, 30kDA, 31kDA (Osp A), 34kDA (Osp B), 39kDA, 45kDA, 58kDA, 66kDA and 93kDA. If any of the Borrelia specific antigen(s) are present in the urine sample, bluish-purple bands are visualized on a membrane. The RWB can be performed as a confirmation test on any presumptive positive LDA sample. *Note: Urine antigen detection tests are currently not available in New York. Neurological Symptoms IgG and/or IgM Western Blot Polymerase Chain Reaction Detection of Borrelia burgdorferi with the Multiplex PCR The multiplex polymerase chain reaction (PCR) is a very specific and sensitive assay for the detection of Borrelia burgdorferi-specific DNA in clinical specimens. Theoretically, the assay can be performed on any sample. B. burgdorferi-specific genomic and plasmid DNA are simultaneously selected, amplified, and detected. A negative result implies only that B. burgdorferi-specific DNA was not detected in the test sample. While the PCRs potential sensitivity is tremendous, the sample tested must contain at least one recoverable organism for the genomic assay, and pieces or blebs of antigen for the plasmid assay. Which tests to perform? Summary There is a logical sequence in selecting laboratory tests to aid in the diagnosis of Lyme disease. Much like the hepatitis model, antigen is present early after initial infection. Later, there is an antibody response in about 70% of patients. IgM appears first and is followed by IgG. There are two different types of antibody assays: the ELISA and the Western Blot. The ELISA is a poor assay, with marginal sensitivity. The Western Blot is the more sensitive test. Recurrent and persistent infections offer a unique diagnostic problem, since the IgG response may be absent. The IgM Western blot may be helpful for some patients with persistent disease, but care must be taken to rule out cross-reactions. During persistent or recurrent disease, assays that detect antigen can be useful. The antigen detection tests and the PCR can be complementary to one another. Antigen detection assays and/or the PCR should be considered for studying the joint fluid, when indicated, and the cerebral spinal fluid, in the presence of neurological symptoms. All assays, including the PCR and the antigen detection, may be required under certain circumstances. IGeneX, Inc. |