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Lyme Antibody SerologyELISALYME IgG/IgM ANTIBODY SEROLOGY The IgG/IgM Antibody Serology test is an ELISA (enzyme linked immunoassay) which indicates the presence of both IgG and IgM antibodies to B. burgdorferi.1,2 The IgG antibody often persists long after symptoms have disappeared. The presence of antibody indicates exposure, not active disease. A positive or equivocal test must be confirmed by both IgG and IgM Western Blots. Current FDA-approved ELISA tests are not as sensitive as they should be. While the concept of these screening tests is good, lack of sensitivity is a drawback. In spite of this, Medicare and 3rd party payers often require these tests to be ordered first.2,4 Lyme disease may begin with a skin lesion at the site of a tick bite from Ixodes scapularis or a related species. A "bull's-eye" lesion, erythema migrans (EM), is characteristic of Lyme disease; however, only 60% of patients positive for Lyme exhibit the rash.3-5 The IgG/IgM ELISA is the most commonly used screening test for the primary diagnosis of Lyme disease. This test is recommended at least four weeks after exposure. Patients with the diagnosis of Lyme disease based on clinical history have positive IgG/IgM serology results within one year of the tick bite approximately 70% of the time. The percentage of patients with a positive serology is reduced in subsequent years.5 Ordering multiple tests, such as the ELISA, Western Blot, Antigen Capture, and PCR, is significantly more efficient in a clinical diagnosis than is any single test.
Figure 2. A typical early symptom of Lyme disease is the slowly expanding bull's-eye red rash, erythema migrans (EM) 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. Because IgM antibodies appear early in response to infection, this test may be positive two to six weeks after exposure.1,2 The level of IgM rapidly declines over time. A positive or equivocal IgM antibody test must be confirmed by an IgM Western Blot. The sensitivity concerns mentioned for the IgG/IgM assay also affect this assay. Appropriate antibiotic therapy during the early stage (the first four months) of Lyme disease can reduce the likelihood of late stage disease. The IgM response may persist in patients with prolonged illness, and a new IgM response may appear late in persistent or recurrent disease, or from re-infection.6 This test is recommended approximately 2 weeks after suspected exposure and should also be ordered late in the disease with the return of acute symptoms.
Figure 3. The spirochete, Borrelia burgdorferi IGeneX, Inc. |
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