The Laboratory Diagnosis of Lyme Disease

ABSTRACTS & COMMENTARY

Sources: American College of Physicians. Position Papers. Clinical Guideline, Part I. Guidelines for laboratory evaluation in the diagnosis of Lyme disease. Ann Intern Med 1997;127:1106-1108; Tugwell P, et al. Clinical Guideline, Part 2. Laboratory evaluation in the diagnosis of Lyme disease. Ann Intern Med 1997;127:1109-1123.

To the neurologist faced with the challenge of diagnosing late manifestations of Lyme disease, serologic testing may cause more confusion than confirmation. Based on a review of English-language medical literature from 1982 to 1996, this position paper from the American College of Physicians offers sorely needed guidelines.

Isolation of the spirochete from tissue or body fluid is the best diagnostic evidence of disease, but, other than erythema migrans (EM) biopsy samples, cultures are usually unsuccessful. Serologic tests include enzyme-linked immunosorbent assay (ELISA), indirect fluorescent antibody immunofluorescent assay, and Western blot. A crucial factor in using these tests is that the common sense likelihood of diagnosis be relatively high (> 20%). Otherwise, the false-positive rate renders the test misleading.

    1. Patients from areas of low or moderate prevalence, with nonspecific symptoms including arthralgias, myalgias, headaches, fatigue, palpitations, and general malaise, should NOT be tested (likelihood of diagnosis < <20%).

    2. Patients who fulfill the American College of Rheumatology diagnostic criteria for fibromyalgia and test positively for Lyme disease do not improve with antibiotic therapy. Testing in such patients is unhelpful.

    3. Patients with a high probability (> 80%) of Lyme disease (with arthritis or rash, or history of rash resembling EM, and previous tick bite), treat empirically with antibiotics.

    4. If the likelihood of Lyme disease is 20-80% (this requires the presence of symptoms and signs consistent with Lyme disease), ELISA is the initial step (IgG titer of 1:800, IgM titer of 1:200, defined as positive). If indeterminate (IgG titers of 1:200 and 1:400, IgM titer of 1:100, less being defined as negative), obtain Western blot testing. If either test is positive, the probability of disease is high, and therapy is warranted. Conversely, if negative, disease probability is low, and therapy is not indicated.

    5. Cerebrospinal fluid (CSF) testing is not necessary to diagnose cases of suspected neuroborreliosis because almost all such patients have positive serum serologic tests.

    6. The immunofluorescent assay is a more difficult test to perform and interpret, with poor reproducibility.

    7. T-cell proliferation assay and polymerase chain reaction tests of serum or CSF require further validation. -mr