Diagnosis and Testing
When assessing a patient for Lyme disease, health care providers should consider:
- The signs and symptoms of Lyme disease
- The likelihood that the patient has been exposed to infected blacklegged ticks
- The possibility that other illnesses may cause similar symptoms
- Results of laboratory tests, when indicated
CDC currently recommends a two-step testing process for Lyme disease. 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).
Key points to remember
- Most Lyme disease tests are designed to detect antibodies made by the body in response to infection.
- Antibodies can take several weeks to develop, so patients may test negative if infected only recently.
- Antibodies normally persist in the blood for months or even years after the infection is gone; therefore, the test cannot be used to determine cure.
- Infection with other diseases, including some tickborne diseases, or some viral, bacterial, or autoimmune diseases, can result in false positive test results.
- 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.
CDC supports the development of new 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). For more details, see: Recommendations for Test Performance and Interpretation from the Second National Conference on Serologic Diagnosis of Lyme Disease.