Borrelia burgdorferi antibodies - serum

IF or EIA for IgG and or IgM antibodies; immunoblot.

IgM antibody becomes positive 2-3 weeks after onset of disease, but should not be used as the sole criterion to diagnose a recent infection as IgM may persist for months or years despite effective antimicrobial therapy.

IgG is usually detectable after one month of active infection.

The EIA has high sensitivity but limited specificity because the antibodies cross react with other spirochaetes.

Positive EIAs should always be confirmed by immunoblot using antigens from both North American and European strains.