Assessment of the reproducibility of oligoclonal IgM band detection for its application in daily clinical practice.

Background: The presence of oligoclonal IgM bands (OCMB) in cerebrospinal fluid (CSF) is an unfavourable prognostic marker in multiple sclerosis. There is no commercial test to investigate OCMB status. However, a sensitive and specific isoelectrofocusing (IEF) and western blot method was described. We aimed to study the inter-centre reproducibility of this technique, a necessary condition for a reliable test to be incorporated into clinical practice.

Methods: The presence of OCMB was analysed by IEF and western blot with prior reduction of pentameric IgM. We assayed the reproducibility of this test in a blinded multicentre study performed in 13 university hospitals. Paired-CSF and serum samples from 52 neurological patients were assayed at every centre.

Results: Global analysis rendered a concordance of 89.8% with a kappa value of 0.71.

Conclusion: These data indicate that OCMB detection by means of IEF and western blot with IgM reduction shows a good interlaboratory reproducibility and thus can be used in daily clinical setting.