Description of the blood test:

The Borrelia IgG test is a serological laboratory examination used to detect immunoglobulin class G antibodies against the bacteria Borrelia burgdorferi. These bacteria are transmitted to humans through the bite of infected black-legged ticks and are the causative agents of Lyme disease. Unlike IgM antibodies, which appear shortly after infection, IgG antibodies typically develop more slowly—usually 4 to 6 weeks after exposure—and can persist in the bloodstream for many years. This test is the primary tool for identifying the disseminated or late stages of the disease and for confirming whether a patient has had a prior encounter with the pathogen.

What does the analysis represent?

• Late-Phase Marker: IgG presence is indicative of the secondary or tertiary stages of Lyme disease, affecting the joints, heart, or nervous system.
• Immune Memory: Confirms long-term immune recognition of the bacteria, though it does not necessarily guarantee permanent immunity against reinfection.
• Diagnostic Confirmation: Used in a two-tier testing system to support a clinical diagnosis of Lyme borreliosis in patients with long-term symptoms.
• Performance: High-precision enzyme immunoassay (ELISA) performed on a venous blood sample.

Recommendations for the test (General)

• Time: Blood collection is best performed during the morning hours.
• Fasting: A food intake pause of at least 4–8 hours is recommended.
• Timing of the Test: Since IgG takes several weeks to develop, testing too early (within the first month of a tick bite) may result in a false negative.
• Important: Provide your physician with a timeline of any known tick bites or the appearance of an “erythema migrans” (bullseye rash), as this helps in interpreting the IgG levels.

What can affect the results?

• Antibiotic Treatment: Early or insufficient antibiotic therapy shortly after a tick bite can sometimes blunt the IgG response, leading to lower-than-expected titers.
• Cross-reactivity: Similar to IgM, IgG tests can occasionally show cross-reactivity with other spirochetes (like syphilis) or autoimmune conditions (like rheumatoid arthritis).
• Serological Scars: IgG antibodies can remain positive for years after successful treatment, meaning a positive test does not always indicate a current active infection.

When to take the test?

• Recommendations: Prescribed for patients with symptoms of late Lyme disease, such as chronic joint swelling (Lyme arthritis), neurological issues (meningitis or facial palsy), or cardiac irregularities (Lyme carditis) that appear weeks or months after potential exposure.
• Preparation: Standard preparation for venous blood collection; avoid alcohol for 24 hours prior to the draw.

How to interpret the results?

The interpretation of data is the exclusive responsibility of an infectious disease specialist or a neurologist. A positive IgG result confirms that the immune system has responded to Borrelia, but it must be correlated with clinical symptoms to determine if the infection is active or historical. Because of potential cross-reactivity, a positive ELISA result is typically confirmed with a Western Blot (Immunoblot) test. Only an expert can differentiate between a “serological scar” and a chronic infection requiring intensive antibiotic therapy.

Possible further investigations

• Borrelia Western Blot (IgG): To confirm the specificity of the antibodies and rule out false positives.
• Cerebrospinal Fluid (CSF) Analysis: If neurological symptoms are present, to check for neuroborreliosis.
• C-Reactive Protein (CRP) and ESR: To assess the level of systemic inflammation.
• Consultation with an Infectious Disease Specialist: To evaluate the stage of the disease and determine the necessity of treatment.

When does the next step make sense?

If Borrelia IgG is detected, it indicates a significant interaction between your immune system and the bacteria. The next step is a consultation with a specialist to determine if your current symptoms are linked to this result and to ensure that any late-stage complications are managed with the correct medical protocol.

👉 If necessary, you can discuss the test results with our specialized — rheumatologist disease specialist (Doctors – TAMC).