Laboratory findings in Lyme Disease

The diagnosis of Lymedisease is made on clinical findings, epidemiologic features, and an elevated antibody response to B burgdorferi. The available laboratory tests (with the exception of a positive culture from an EM lesion) can be unreliable. Serologic testing only should be undertaken when clinical and epidemiologic features suggest Lymediseaseas the diagnosis.

Most patients with B burgdorferi are found to have detectable antibodies when tested with enzyme-linked immunosorbent assay (60-70% within 2-4 weeks of infection and 90% by the disseminated and persistent stages). However, serologic tests lack standardization, their accuracy is often unsubstantiated, and false-positive results are common. IgM antibody appears 2-4 weeks after the EM lesion, peaks at 6-8 weeks, and declines after 4-6 months. IgG antibody appears 6-8 weeks after the EM lesion, peaks at 4-6 months, and remains at low levels despite antibiotic therapy. A fourfold rise in antibody titer would be suggestive of recent infection. Western blot analysis is used to confirm results obtained by enzyme-linked immunosorbent assay.

The finding that a patient has significant amounts of anti-B burgdorferi-specific antibodies can be interpreted only in the context of the clinical setting. Demonstrating that a patient has an immune response against this organism does not mean that the patient is actively infected or that any symptoms are necessarily related to B burgdorferi infection. Detection of spirochetal DNA by PCR is useful in synovial fluid (75-85% of sensitivity). However, the sensitivity of PCR in CSF, blood, or urine samples has not been well established.