[Retrospective study of Lyme borreliosis positive serologies in 2003]

To estimate the percentage of positive sera for Lyme borreliosis antibodies, to precise the characteristics of clinical cases diagnosed from serological data and to determine their geographical distribution in France.

Studied sera were those received by the Pasteur-Cerba laboratory in 2003. IgG and IgM isotypes were detected using the Dade Behring kits. Antibody specificity was analysed with the Meridian's western blot.

1504/16 176 (9%) sera were positive for IgG isotype, and 978/3298 (29%) for IgM. The specificity was confirmed by western blot in 49% cases for IgG and in 54% for IgM. The highest positive serology rates were found in eastern and centre regions and in Aquitaine. Forty-two cases have been investigated leading to the identification of 16 borreliosis cases, each suffering of an erythema migrans. Five of them had neurological signs. Patient mean age was 40 years. 87% of patients had risk factors and 69% reported previous tick bites, mainly on lower limbs.

A low rate of positive borreliosis sera was found, suggesting that serology prescription should be limited to patients suffering of compatible clinical signs, as recommended by the EUCALB. Erythema migrans was the most frequent clinical manifestation and neurological signs were present in 30% of cases. Finally, the geographical case distribution was similar to that provided by the study of the Sentinelle network in 1999-2000.