Clinical Testing and Diagnosis for Lyme Disease

Key points

  • Laboratory diagnosis of Lyme disease relies on serologic testing for antibodies to Borrelia burgdorferi.
  • CDC recommends a two-step serologic testing process using FDA-cleared assays.
  • Serologic assays may be falsely negative during the first 4-6 weeks after infection.
  • Before CDC will recommend new tests, they must be cleared by the Food and Drug Administration (FDA).
Borrelia burgdorferi under a microscope

Considerations

When assessing a patient for Lyme disease, healthcare providers should consider:

  • The likelihood that the patient has been exposed to infected blacklegged ticks
  • Whether the patient's signs and symptoms are clinically consistent with Lyme disease
  • The possibility that other illnesses may cause similar symptoms
  • Results of laboratory testing, when indicated

Recommended tests

CDC currently recommends a two-step testing process for Lyme disease serologic testing. Both steps are required and can be done using the same blood sample. If this first step is negative, no further testing is recommended. If the first step is positive or indeterminate (sometimes called “equivocal”), the second step should be performed. The overall result is positive only when the first test is positive (or equivocal) and the second test is positive (or for some tests equivocal). Standard two-tier testing (STTT) uses enzyme immunoassay (EIA) as the first step and western blotting (WB) for the second step. Increasingly, laboratories are using modified two-tier testing (MTTT) in which both assays are EIAs.

For more information, see: Updated CDC Recommendation for Serologic Diagnosis of Lyme Disease and APHL Guidance and Interpretation of Lyme Disease Serologic Test Results.

Key points to remember

  • Most Lyme disease tests are serologic assays designed to detect antibodies that can take several weeks to develop following infection; patients may test negative if recently infected.
  • Once elevated, antibody titers will remain so for months to years and cannot be used to determine cure.
  • False positive cross-reactions may occur in patients with other conditions, including relapsing fever, syphilis, rheumatoid arthritis, and Epstein-Barr virus infection.
  • Some tests give results for two types of antibody, IgM and IgG. Positive IgM results should be disregarded if the patient has been ill for more than 30 days.
  • Patients who receive antibiotic treatment early in disease may be less likely to seroconvert.

Additional serologic testing resources available here.

Other tests

New tests may be developed as alternatives to one or both steps of the two-step process. Before CDC will recommend new tests, they must be cleared by the Food and Drug Administration (FDA).

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Content Source:
National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)