Borrelia IgG (Lyme) – Marker of Past Exposure

What Is Borrelia IgG (Lyme)?

Borrelia IgG (Lyme) antibodies are IgG-class antibodies produced by the immune system in response to *Borrelia burgdorferi*, the bacterium that causes Lyme disease. They typically appear several weeks after infection and can persist for years. The test is performed on venous blood using serology methods.

How Are Results Interpreted?

Results are reported as positive, negative, or equivocal. The exact cut-off values are laboratory-dependent. A two-tier testing approach is standard: an initial ELISA screening is followed by a confirmatory Western blot if the ELISA result is positive or equivocal.

What Can a Positive Result Mean?

A positive result may indicate past exposure to *Borrelia* bacteria. IgG antibodies can persist for years even after successful treatment. A positive result should always be evaluated together with your current symptoms and clinical history.

What Can a Negative Result Mean?

A negative result may indicate no prior contact with *Borrelia*, or that testing was performed too early. Antibodies take several weeks to develop after infection. In rare cases, individuals with immunosuppression may not produce detectable antibodies.

What to Do Next

Discuss your result with your doctor. If the result is positive, a Western blot confirmation and IgM testing are typically recommended. If the result is negative but you have had a recent tick bite, your doctor may advise repeating the test after a few weeks.

Follow-Up and Monitoring

Borrelia IgG antibodies persist for a long time and are not suitable for monitoring treatment response. Prevention through tick protection measures remains more important than repeated testing.

Questions to Ask Your Doctor

• Does my result indicate an active infection or only past exposure?
• Is a Western blot confirmation needed?
• How do my current symptoms relate to this result?
• Could the timing of exposure affect the reliability of this result?
• Should I repeat this test, and if so, when?