What lab tests are used to diagnose Lyme disease?

Laboratory Testing for Lyme Disease Diagnosis

The standard laboratory approach for diagnosing Lyme disease is a two-tiered serologic testing algorithm consisting of an enzyme-linked immunoassay (EIA/ELISA) or immunofluorescence assay (IFA) followed by a Western immunoblot if the first test is positive or equivocal. 1

Two-Tiered Testing Protocol

First-Tier Test

• Enzyme-linked immunoassay (EIA/ELISA) or Immunofluorescence assay (IFA)
  • Measures overall antibody response (IgM and IgG) to B. burgdorferi antigens
  • EIA is more commonly used as it can be automated and provides quantitative results
  • Most labs use whole-cell sonicate preparation of B. burgdorferi as antigen
  • Newer EIAs use specific antigens like VlsE lipoprotein or C6 peptide for higher specificity

Second-Tier Test (if first tier is positive or equivocal)

• Western immunoblot (WB)
  • Detects antibodies against specific B. burgdorferi proteins
  • IgM and IgG immunoblots are interpreted separately using standardized criteria
  • For suspected early infection (<30 days), both IgM and IgG immunoblots are performed
  • For longer duration (>30 days), only IgG immunoblot is recommended

Test Performance and Limitations

Sensitivity by Disease Stage

• Early localized disease (erythema migrans):
  • Only 30-40% sensitivity during acute phase
  • Increases to 60-70% in convalescent phase (3-4 weeks later) 1, 2
• Early disseminated disease:
  • Higher sensitivity (70-80%) for patients with disseminated infection 1
• Late disseminated disease (arthritis, neurologic manifestations):
  • Very high sensitivity (>95%) 1, 2

Specificity

• Two-tiered testing has >95% specificity when properly performed 1
• Western immunoblot significantly reduces false positives from the first-tier test 3

Important Clinical Considerations

1. Erythema migrans (EM) rash: Patients with typical EM rash and appropriate epidemiologic exposure should be diagnosed clinically without laboratory testing 1

2. Timing matters: Antibody response develops gradually after infection

   • False negatives are common in early disease
   • Repeat testing 3-4 weeks after symptom onset if early Lyme disease is suspected but initial tests are negative 1, 2

3. Antibody persistence: Antibodies often persist for months or years after successful treatment, so positive serology cannot distinguish active from past infection 1

4. Cross-reactivity: False positives can occur in patients with other conditions:

   • Syphilis
   • Epstein-Barr virus infection
   • Other spirochetal diseases 1, 4

5. When NOT to test:

   • Patients with nonspecific symptoms without appropriate exposure history 1
   • Patients with typical amyotrophic lateral sclerosis, multiple sclerosis, Parkinson's disease 1
   • Patients with psychiatric illness 1
   • Children with developmental or behavioral disorders 1

Newer Testing Approaches

• Two-EIA algorithm: Using two different EIAs sequentially (e.g., whole-cell sonicate EIA followed by C6 peptide EIA) shows comparable sensitivity and specificity to standard two-tiered testing 1

• Microarray immunoblot assays: Automated platforms like ViraChip show comparable agreement with traditional Western blot methods with potential time savings 5

Common Pitfalls to Avoid

1. Testing too early: Testing during the first few days of infection often yields false negatives

2. Over-reliance on serology for early disease: Clinical diagnosis based on EM rash is more reliable than serology in early disease

3. Misinterpreting persistent antibodies: Positive serology after treatment does not indicate treatment failure or persistent infection

4. Indiscriminate testing: Testing patients with nonspecific symptoms and low pretest probability leads to false positives and unnecessary treatment

5. Using non-validated tests: Stick to FDA-cleared tests and standardized interpretation criteria

Remember that serologic testing is most useful for confirming infection in patients with objective clinical findings consistent with later stages of Lyme disease, while early localized disease with EM rash should be diagnosed clinically.