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Lyme disease is caused by the spirochete Borrelia burgdorferi. The spirochete is transmitted to humans through the bite of Ixodes species ticks. Endemic areas for Lyme disease in the United States (US) correspond with the distribution of 2 tick species, Ixodes dammini (Northeastern and Upper Midwestern US) and Ixodes pacificus (West Coast US). In Europe, Ixodes ricinus transmits the spirochete.
Lyme disease exhibits a variety of symptoms that may be confused with immune and inflammatory disorders. Inflammation around the tick bite causes skin lesions. Erythema chronicum migrans (ECM), a unique expanding skin lesion with central clearing that results in a ring-like appearance, is the first stage of the disease. Any of the following clinical manifestations may be present in patients with Lyme disease: arthritis, neurological disease, cardiac disease, or skin lesions. Neurologic and cardiac symptoms may appear with stage 2 and arthritic symptoms with stage 3 of Lyme disease. In some cases, a definitive distinction between stages is not always seen. Further, secondary symptoms may occur even though the patient does not recall a tick bite or a rash.
Serology may not be positive until 2 to 4 weeks after onset of ECM; however, culture of skin biopsies obtained near the margins of ECM are frequently positive. In late (chronic) stages of the disease, serology is often positive and the diagnostic method of choice. PCR testing also may be of use in these late stages if performed on synovial or cerebrospinal fluid.
Early antibiotic treatment of Lyme disease can resolve clinical symptoms and prevent progression of the disease to later stages. Treatment with penicillin, tetracycline, erythromycin, chloramphenicol, or ceftriaxone is considered appropriate therapy
The Second National Conference on the Serologic Diagnosis of Lyme Disease (1994) recommended that laboratories use a 2-test approach for the serologic diagnosis of Lyme disease. Accordingly, specimens are first tested by the more sensitive EIA or enzyme-linked immunosorbent assay (ELISA). A Western blot (WB) assay is used to confirm positive Lyme EIA or ELISA results due to the presence of IgG or IgM class antibodies. WB identifies the specific proteins to which the patient's antibodies bind. Although there are no proteins that specifically diagnose Borrelia burgdorferi infection, the number of proteins recognized in the WB assay is correlated with diagnosis.
Diagnosing Lyme disease
As a sensitive screening (enzyme-linked immunosorbent assay) test for Lyme disease
Negative result: no antibody to Borrelia burgdorferi detected. This result does not exclude the possibility of Borrelia burgdorferi infection. Patients in early stages of infection may not produce detectable levels of antibody. According to the manufacturer’s package insert, antibiotic therapy in early disease may prevent antibody production from reaching detectable levels. Patients with clinical history and/or symptoms suggestive of Lyme disease or where early Lyme disease is suspected, but with negative test results should be retested in 2 to 4 weeks.
Equivocal result: the imprecision inherent in any method implies a lower degree of confidence in the interpretation of specimens with absorbance values very close to the calculated cutoff value. For this reason an equivocal category has been designated. Equivocal specimens will be tested by Western blot (WB) assays in accordance with Centers for Disease Control and Prevention (CDC)/Association of Public Health Laboratories (APHL) recommendations.
Positive result: antibody to Borrelia burgdorferi detected. All positive results will be supplemented by retesting the serum by WB for the detection of IgG and IgM antibodies to Borrelia burgdorferi, in accordance with CDC/APHL recommendations.
A negative result does not exclude the possibility of infection with Borrelia burgdorferi.
A positive result is not definitive evidence of infection with Borrelia burgdorferi. It is possible that other disease conditions, including syphilis, periodontal disease, rheumatoid arthritis, systemic lupus erythematosus, and other autoimmune diseases, may produce artifactual reactivity in the assay.
This test should not be used to screen the general population. The predictive value of the assay is a function of the pretest probability of Lyme disease in the population tested. Hence, only patients with clinical symptoms of Lyme disease or suspected exposure to Borrelia burgdorferi should be tested.
1. Dattwyler RJ: Lyme borreliosis: an overview of clinical manifestations. Lab Med 1990;21:290-292
2. Schwan TG, Burgdorfer W, Rosa PA: Borrelia. In Manual of Clinical Microbiology. Seventh edition. Edited by PR Murray. Washington, DC, ASM Press, 1999, pp 746-758
3. CDC: Recommendation for test performance and interpretation from second national conference on serological diagnosis of lyme disease. MMWR Morb Mortal Wkly Rep 1996;45:481-484
4, Package insert: Immunetics C6 B burgdorferi (Lyme) ELISA Kit, Immunetics, Inc, Boston, MA 02210-2377, 2013