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Abstract: 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). [Copyright &y& Elsevier]

Abstract: Very sensitive and allowing discrimination between IgG and IgM, the enzyme immunoassays are the most commonly used to carry out viral serologies. The presence of IgG corresponding to a natural or postvaccination immune status or to a latent or occult infection is a reliable information to assess the protection against some opportunistic or teratogenic infections respectively in children or pregnant women. The search of IgM by immunocapture is suitable to early diagnose the majority of common viral diseases in childhood, specially when presenting in an atypical form, and to attest a congenital rubella infection. Moreover, IgG avidity proved to be useful in dating an infection and confirming positive IgM results. However, viral infections localized at an entry site of the host, such as respiratory and enteric diseases, as well as syndromes of herpes simplex and enteroviral origin, do not represent indications of serological diagnosis. Provided its use with discernment, the serological diagnosis of viral infections have to be considered as a high performance and of low cost biological tool. [Copyright &y& Elsevier]