What labs are needed to rule out Lyme disease?

Laboratory Testing for Lyme Disease

To rule out Lyme disease, a two-tiered serologic testing approach is recommended, consisting of an enzyme-linked immunosorbent assay (ELISA) or immunofluorescence assay (IFA) as the first tier, followed by a Western immunoblot test if the first test is positive or equivocal. 1

Two-Tiered Testing Algorithm

First Tier Testing

• ELISA or IFA: These tests measure the overall antibody response (IgM and IgG) to Borrelia burgdorferi antigens
  • Most laboratories use whole-cell sonicate preparation of B. burgdorferi
  • Newer EIAs using specific antigens like VlsE lipoprotein or C6 peptide are also FDA-cleared and offer higher specificity 1
  • If the result is negative, no further testing is needed
  • If the result is positive or equivocal, proceed to second tier testing

Second Tier Testing

• Western Immunoblot: This confirmatory test detects antibodies against specific B. burgdorferi proteins
  • IgM Western blot: Useful in early infection (first 30 days)
  • IgG Western blot: More reliable for later stages of infection
  • Interpretation follows standardized criteria established at the 1994 Second National Conference on the Serologic Diagnosis of Lyme Disease 1

Timing Considerations

The timing of testing is crucial for accurate results:

• Early localized disease (within 30 days of tick bite):

  • Serologic testing has low sensitivity (20-50%)
  • Patients with erythema migrans (EM) rash in endemic areas can be diagnosed clinically without laboratory testing 1

• Early disseminated disease (weeks after infection):

  • Sensitivity of two-tiered testing improves to approximately 70-80% 1
  • IgM antibodies typically appear first, followed by IgG

• Late disseminated disease (months after infection):

  • Sensitivity of two-tiered testing reaches 90-100% 1
  • IgG antibodies should be present; isolated IgM positivity is likely false positive

Important Caveats

1. False negatives: Early antibiotic treatment can blunt or prevent antibody response 1

2. False positives: Can occur with other conditions including:

   • Syphilis
   • Infectious mononucleosis (EBV/CMV)
   • Autoimmune disorders
   • Other spirochetal infections 1

3. Persistent antibodies: Antibodies often persist for months or years after successfully treated infection, so seroreactivity alone cannot be used as a marker of active disease 1

4. Limitations of other testing methods:

   • PCR testing of blood, CSF, or synovial fluid has not been standardized for routine diagnosis 1
   • Culture of B. burgdorferi requires special media and extended observation, limiting clinical utility 1

Special Considerations

• For suspected neuroborreliosis, paired serum and CSF antibody testing may be helpful
• Newer testing approaches using multiple recombinant antigens or peptide-based ELISAs may improve diagnostic accuracy, but the standard two-tiered approach remains the recommended method 1
• IgA testing is not routinely recommended as there are insufficient data to demonstrate its clinical utility 1

Remember that laboratory results should always be interpreted in the context of the patient's clinical presentation, exposure history, and epidemiological risk factors.