Diagnosis of Lyme disease

Lyme disease is often difficult to diagnose because its symptoms and signs mimic those of so many other diseases. The fever, muscle aches, and fatigue of Lyme disease can easily be mistaken for viral infections, such as influenza or infectious mononucleosis. Joint pain can be mistaken for other types of arthritis, such as rheumatoid arthritis, and neurologic signs can mimic those caused by other conditions, such as multiple sclerosis. At the same time, other types of arthritis or neurologic diseases can be misdiagnosed as Lyme disease.

The clinical diagnosis of Lyme disease is usually based on history of possible exposure to ticks, especially in areas where Lyme disease is known to occur and a combination of symptoms and signs of infection. Serodiagnosis to detect anti-borrelia antibodies is not useful until in later stages of illness. Serologic testing may, however, provide valuable supportive diagnostic information in patients with endemic exposure and/or clinical findings that suggest late stage or disseminated Lyme disease.

When serologic testing is indicated, CDC recommends testing first with an enzyme-linked immunosorbent assay (ELISA) or an indirect fluorescent antibody (IFA) test, followed by a more specific Western immunoblot (WB) test to corroborate equivocal or positive results obtained with the first test. None of these tests is useful in the diagnosis of early stages of Lyme disease since a primary serum immune response is just beginning. Furthermore, these tests are associated with a high degree of cross-reactivity, since sera from patients with Rocky Mountain spotted fever, relapsing fever, mononucleosis, syphilis, and rheumatoid arthritis often test positive for Lyme disease.

Patients with early disseminated or late-stage disease usually have strong serological reactivity. Antibodies may persist for months or years following successfully treated or untreated infection. Thus, seroreactivity alone cannot be used as a marker of active disease.

Neither a positive serologic activity nor a history of previous Lyme disease assures that an individual has protective immunity. Repeated infection with B. burgdorferi has been documented.

B. burgdorferi can be cultured from 80% or more of biopsy specimens taken from early erythema migrans lesions. However, the diagnostic value of this procedure is limited because of the need for special bacteriologic media (BSK medium) and protracted observation of cultures.

The polymerase chain reaction (PCR) has been used to amplify genomic DNA of B. burgdorferi in skin, blood, cerebrospinal fluid, and synovial fluid, but PCR has not been standardized for routine diagnosis of Lyme disease.