Clinical Relevance of Different IgG and IgM Serum Antibody Responses to Borrelia burgdorferi After Antibiotic Therapy for Erythema Migrans

OBJECTIVES: To investigate the kinetics of anti-Borrelia burgdorferi antibodies for a minimum of 1 year after antibiotic therapy in patients with erythema migrans (EM) and to correlate antibody titer kinetics with clinical variables. DESIGN: Retrospective study of serial anti-B burgdorferi antibodies in correlation to clinical variables. SETTING: University-based hospital. PATIENTS: One hundred thirteen patients with EM. INTERVENTIONS: Pretreatment and a median of 4 consecutive posttreatment serum samples from median follow-up of more than 400 days were simultaneously investigated for anti-B burgdorferi IgG and IgM antibodies. Semiquantitative titers were plotted to identify different groups of antibody kinetics. Individual patients were then stratified to those groups according to their antibody development. A statistical comparison of clinical and therapy-related characteristics among the serologic groups was performed. RESULTS: Anti-B burgdorferi IgG and IgM antibody titers developed in 3 distinct courses: persistent positivity across follow-up (IgG: 12 patients, 11%; IgM: 14, 12%), persistent negativity (IgG: 63, 56%; IgM: 47, 42%), and decrease of a positive pretreatment titer to a negative titer approximately 5 months after therapy (IgG: 34, 30%; IgM: 49, 43%). Statistics revealed significant correlations only between persistent positive IgG titers and long disease duration or large EM lesions before therapy. CONCLUSIONS: Long duration or large size of EM before therapy correlates with persistence of a positive anti- B burgdorferi IgG antibody titer after therapy. Serologic profiles do not depend on the type or duration of therapy or the clinical course thereafter. Thus, antibody testing in the follow-up of patients with EM is inappropriate for the assessment of therapeutic response.