Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to site content Skip directly to page options
CDC Home

Two-step Laboratory Testing Process

CDC currently recommends a two-step process when testing blood for evidence of antibodies against the Lyme disease bacteria. Both steps can be done using the same blood sample.

The first step uses a testing procedure called “EIA” (enzyme immunoassay) or rarely, an “IFA” (indirect immunofluorescence assay).  If this first step is negative, no further testing of the specimen is recommended. If the first step is positive or indeterminate (sometimes called "equivocal"), the second step should be performed.  The second step uses a test called an immunoblot test, commonly, a “Western blot” test. Results are considered positive only if the EIA/IFA and the immunoblot are both positive.

The two steps of Lyme disease testing are designed to be done together.  CDC does not recommend skipping the first test and just doing the Western blot.  Doing so will increase the frequency of false positive results and may lead to misdiagnosis and improper treatment.

New tests may be developed as alternatives to one or both steps of the two-step process. Before CDC will recommend new tests, their performance must be demonstrated to be equal to or better than the results of the existing procedure, and they must be FDA approved. For more details, see: Recommendations for Test Performance and Interpretation from the Second National Conference on Serologic Diagnosis of Lyme Disease.

Image: Two-tier testing figure

Two-tier testing decision tree (Click for larger image)

 
Contact Us:
  • Centers for Disease Control and Prevention
    Bacterial Diseases Branch
    Foothills Campus
    Fort Collins, CO 80521
  • 800-CDC-INFO
    (800-232-4636)
    TTY: (888) 232-6348
  • Contact CDC–INFO
USA.gov: The U.S. Government's Official Web PortalDepartment of Health and Human Services
Centers for Disease Control and Prevention   1600 Clifton Rd. Atlanta, GA 30333, USA
800-CDC-INFO (800-232-4636) TTY: (888) 232-6348 - Contact CDC–INFO
A-Z Index
  1. A
  2. B
  3. C
  4. D
  5. E
  6. F
  7. G
  8. H
  9. I
  10. J
  11. K
  12. L
  13. M
  14. N
  15. O
  16. P
  17. Q
  18. R
  19. S
  20. T
  21. U
  22. V
  23. W
  24. X
  25. Y
  26. Z
  27. #