Borrelia antibodies in children evaluated for Lyme neuroborreliosis

We wanted to elucidate the value of Borrelia antibodies in serum and cerebrospinal fluid (CSF) for the diagnosis of Lyme neuroborreliosis (LNB).

We analyzed the serological findings, by anti-flagellin assay, in 267 patients with neurological symptoms from the Stockholm area, where Lyme borreliosis is endemic.

In the 70 children with LNB, intrathecal Borrelia antibody production was diagnostic and found in 50 (71%). Sixteen (23%) showed an elevated antibody titer in serum only, and 4 (7%) had no serologic findings. Borrelia IgG in serum, with or without concomitant IgM, was a specific (98%), but insensitive (43%) marker of infection. Isolated, false-positive serum IgM titers were common and found in 10 of 67 children (15%) with viral meningitis, as well as in 28 of 111 (25%) with various neurological symptoms and normal CSF. The specificity of an isolated Borrelia IgM titer in serum was 81%, and the positive predictive value for Borrelia infection only 50% in our material. On the other hand, absence of antibodies in blood had a negative predictive value of 94%, which increased to 97% if also CSF findings were included.

Intrathecal antibody production is strongly supportive of an LNB diagnosis. Conversely, isolated, elevated levels of Borrelia IgM in serum occur in up to one-fourth of children with various neurological complaints, and should be interpreted with caution, especially in nonendemic areas.