How is Lyme disease diagnosed?
-
How is Lyme disease diagnosed?
-
@wolfrun In most patients with erythema migrans, a carefully elicited history (including definitions of epidemiologic context) and a physical examination are all that is required to establish the diagnosis of Lyme disease. However, although many patients with Lyme disease present with erythema migrans, others first present with extracutaneous symptoms. In those cases, erythema migrans may never have occurred, may not have been recognized by the patient, or may not have been correctly diagnosed by the physician.
There can be a tendency to overdiagnose Lyme disease, especially in patients with a lifestyle that puts them in a high-risk category. Performing tests when the prior probability of disease is low increases the likelihood of false-positive results. The best way to avoid problems with diagnosis is to follow the Centers for Disease Control and Prevention (CDC) guidelines regarding diagnosis (see Workup), to use a reputable laboratory with experience in testing for Lyme disease, and to obtain the assistance of an infectious disease expert when any questions arise.
Because interpretation of testing is related to stage of disease and requires a two-stage test, laboratory results are often misinterpreted. Clinicians unfamiliar with Lyme disease or Lyme testing may falsely exclude the diagnosis by testing too early in the disease course, or falsely diagnose disease by following up negative enzyme immunoassay (EIA) results with Western blot testing (the latter is indicated only in patients with a positive or indeterminate EIA result).
In addition, separating false-positive antibody tests from asymptomatic infection is impossible. Approximately 5-10% of patients in endemic areas have positive antibody results without a history of symptoms.
Unfortunately, antibodies induced by the infection are not protective against further exposures to Borrelia burgdorferi; therefore, reinfection easily could be confused with a recurrence. Because antibodies may persist for years following an infection, repeat infection is a difficult diagnosis without specific signs of Lyme disease (eg, erythema migrans). Increasing titers after adequate treatment certainly raises suspicion of an active infection, but this is not a reason to repeat posttreatment titers, as they may remain positive for many years.