From the Research
Lyme serology typically becomes positive 2-4 weeks after the tick bite and development of erythema migrans (EM). During the early localized stage of Lyme disease when the EM rash first appears, antibody tests are often negative because the immune system hasn't had sufficient time to produce detectable antibodies against Borrelia burgdorferi, the bacterium causing Lyme disease 1. This delay in seroconversion means that patients with early Lyme disease and a characteristic EM rash should receive treatment based on clinical presentation without waiting for serologic confirmation.
Key Points to Consider
- The two-tier testing approach (ELISA followed by Western blot) becomes increasingly sensitive as the infection progresses, with approximately 70-80% sensitivity during early disseminated disease and >95% sensitivity during late disease 2.
- IgM antibodies typically appear first, within 1-2 weeks after infection, while IgG antibodies develop more slowly, usually becoming detectable 2-4 weeks after infection and peaking at 6-8 weeks 3.
- Patients treated early with antibiotics may never develop positive serology since the immune response may be blunted by early elimination of the pathogen 4.
Clinical Implications
- Diagnosis of erythema migrans is made clinically, and serologic analyses often yield false-negative results and are not required for the diagnosis 1.
- Antibacterial treatment is necessary in all patients to eliminate the spirochete, cure current disease, and prevent late sequelae 2.
- Oral doxycycline, also effective against coinfection with Anaplasma phagocytophilum, is the mainstay of therapy of cutaneous manifestations of Lyme borreliosis 2.