[Laboratory methods for the diagnosis of clinical forms of Lyme borreliosis].

Methods used to diagnose Lyme borreliosis (LB) vary according to clinical presentations. A very good basis to clarify this nosological and clinical entity is the study published by the "European Concerted Action on Lyme Borreliosis" (EUCALB). In fact, only few studies were performed on cohorts of patients including all clinical forms of LB. For Erythema migrans, serology sensitivity is low (20% to 50%), while the sensitivity of culture or PCR reaches 50%. In early-complicated forms, serology is more sensitive (70 to 90%) with the presence of concomitant IgG and IgM. Screening for antibodies in CSF is very useful for the diagnosis of neuroborreliosis. For this clinical form, culture or PCR sensitivity is disappointing (10 to 30%). In arthritis and acrodermatitis chronica atrophicans (ACA), IgG serology is 100% positive with very high titers; however IgM serology is only positive in 5 to 10% of the cases. In ACA, culture sensitivity ranges from 20 to 60% and PCR sensitivity from 60 to 90%. Specificity of antibodies, natural exposure to the etiologic agent, and cross-reactivity are critical for the final interpretation of serological assessment. Only the use of "serological profiles" allows the exploitation of detailed results (isotypes, intensity). In this approach, IgG avidity could be constructive. The western-blot is intended to confirm the specificity of antibodies found in screening methods (Elisa).