Lyme Disease (Borrelia burgdorferi) Antibodies (ELISA) Blood Test

Borrelia IgM antibodies are the first antibodies produced by the immune system in response to Borrelia burgdorferi infection. They typically appear 2–4 weeks after infection and may remain detectable for several months. What Positive Means: A positive Borrelia IgM result suggests recent or current Lyme disease infection. However, IgM results should be interpreted with caution as false positives can occur. Positive or equivocal ELISA results are typically confirmed with Western blot testing. If confirmed positive, antibiotic treatment is indicated. What Negative Means: A negative Borrelia IgM result suggests no recent infection, but does not exclude Lyme disease if testing was performed very early (within the first 2–4 weeks after infection) before antibodies had developed. If clinical suspicion is high, repeat testing may be recommended.

Borrelia IgG antibodies develop later in the immune response, typically appearing 4–6 weeks after infection. They persist longer than IgM antibodies and may remain detectable for months to years after infection, even after successful treatment. What Positive Means: A positive Borrelia IgG result indicates current or past Borrelia infection. In someone with symptoms consistent with Lyme disease, this supports the diagnosis. In someone without current symptoms, a positive IgG may represent past infection (treated or untreated) rather than active disease. Clinical correlation is essential. What Negative Means: A negative Borrelia IgG result suggests no current or past Borrelia infection, or that the test was performed too early in the course of infection (before IgG antibodies developed). If IgM is positive but IgG is negative, this suggests early infection. Interpreting Results Together: IgM positive with IgG negative suggests early infection (first few weeks). Both IgM and IgG positive suggests recent infection or active disease. IgM negative with IgG positive may indicate past infection or late/chronic disease. Both negative with early testing may require repeat testing if symptoms persist.