Laboratory tests are important for establishing the diagnosis in many patients with suspected Lyme disease who do not recall a tick bite and did not notice it or do not have erythema migrans.
The US Centers for Disease Control and Prevention (CDC) recommends a two-step testing procedure. The first step typically consists of a screening enzyme immunoassay (EIA) or enzyme-linked immunosorbent assay (ELISA); if results are positive or equivocal, a Western immunoblot test is performed to confirm the results. In July 2019, the US Food & Drug Administration (FDA) approved the use of concurrent or sequential EIA testing for diagnosis of Lyme disease. The FDA approved the new indication on the basis of data from clinical studies showing that this alternative approach, referred to as a modified two-tier test, is as accurate as testing with EIA or immunofluorescence assay plus Western blot.
The most widely used tests for Lyme disease are antibody detection tests, which can demonstrate that a patient has been exposed to B burgdorferi but cannot confirm infection. The clinical diagnosis is supported by the presence of typical clinical manifestations and laboratory results suggestive of current disease activity (eg, elevated synovial and spinal fluid cell counts).
Routine use of sequential serologic testing in individual patients with early Lyme disease should be discouraged. In addition, acute and convalescent-phase serologic testing has no role in Lyme disease. Because titers may remain elevated for extended periods (as can the positivity of Western blots), convalescent testing is not helpful.
Even if the tick that bit the patient is available, testing the tick for B burgdorferi is not recommended. The presence or absence of B burgdorferi in an Ixodes tick does not reliably predict the likelihood of Lyme disease.
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Cite this: Herbert S. Diamond. Fast Five Quiz: Lyme Disease Practice Essentials - Medscape - Feb 25, 2021.