Is IgM of diagnostic value in case of delayed intrathecal production of IgG antibodies

: The neurological manifestations of Lyme borreliosis comprise a wide range of clinical signs. However, these symptoms might have other aetiologies. Therefore detection of intrathecal production of specific antibodies is necessary to confirm the clinical assumption of neuroborreliosis (NB). In case of delayed intrathecal production of specific IgG antibodies, detection of IgM could play a role in the early diagnosis of NB. To clarify whether IgM is of diagnostic value in such cases, paired CSF serum samples from 176 patients with suspected NB admitted to the department of Neurology, Karl Franzens University, Graz, Austria, were tested. Testing was performed with the IDEA Neuroborreliosis Kit (Dako, Denmark) and Enzygnost Borreliosis (Behring, Germany) and results of both methods were compared. According to well defined criteria 63 of the 176 patients had defined NB and 113 were regarded as possible NB. Twelve out of 63 patients with defined NB had delayed intrathecal IgG production. Only one patient with delayed IgG production had an intrathecal IgM production prior to IgG. In all patients with possible NB no intrathecal production of IgM was detected. At the time of the first lumbar puncture IgG intrathecal production could be detected with the IDEA seven times more often than with the Enzygnost Borreliosis. The determination of intrathecal production of IgM does not appear to be of diagnostic value in patients with delayed IgG antibody production. Therefore a consecutive lumbar puncture is more likely to confirm clinical assumption if there is strong clinical evidence of NB.