Borrelia burgdorferi Ab (Lyme ELISA)

What is Borrelia burgdorferi Ab (Lyme ELISA)?

Screens for antibodies against Borrelia burgdorferi, the bacterium that causes Lyme disease, as the first step of two-tier testing.

This ELISA (or similar screening immunoassay) detects antibodies against Borrelia burgdorferi, the bacterium spread by blacklegged tick bites that causes Lyme disease. It relates to the immune system and can involve the skin, joints, nervous system, and heart depending on disease stage. Clinicians commonly order it after a tick bite, exposure in an endemic area, or symptoms such as a rash, fever, or joint pain, especially when the classic erythema migrans rash is not present or its cause is uncertain. Per CDC-recommended two-tier testing, a positive or equivocal ELISA is typically followed by a Western blot to confirm the result, since the ELISA alone is a screening test with a higher chance of false positives.

Tests often checked alongside this

• Borrelia burgdorferi IgG Western Blot — the confirmatory test used when ELISA is positive or equivocal
• Borrelia burgdorferi IgM Western Blot — considered for suspected recent infection
• Anaplasma phagocytophilum Ab — a common tick-borne co-infection
• Babesia microti Ab — another possible co-infection from the same tick bite

How this can show up in how you look and feel

• May be associated with a rash, sometimes described as a bullseye pattern, at the site of a tick bite
• May be associated with fever, chills, headache, fatigue, or muscle and joint aches
• May be associated with joint swelling or neurological symptoms in later, untreated stages

What can affect this marker

• Timing of testing relative to tick bite or symptom onset
• Prior Lyme disease or other Borrelia exposure, which can keep antibodies detectable long-term
• Immune status
• Lab-to-lab variability in assay methods

What to track over time

• Whether an equivocal or positive ELISA is confirmed by Western blot
• How results align with the timeline of the tick bite and symptoms
• Whether repeat testing several weeks after exposure is useful if the first test was early
• Any changes in symptoms over time alongside test results

What to ask your doctor

• Does my result warrant a Western blot for confirmation?
• How does the timing of my tick bite affect how this result should be interpreted?
• Could my symptoms have another explanation?
• Should I be tested for other tick-borne infections as well?

This glossary entry is for informational purposes only and is not a substitute for professional medical advice. Read our Terms of Use.