How do you interpret conflicting findings on CSF immunoglobulin tests for work up of multiple sclerosis and its mimics?

Although the specific role of cerebrospinal fluid (CSF) testing has evolved in the successive revisions of the McDonald criteria, it remains an important part of the evaluation of suspected multiple sclerosis (MS), both to provide support for the diagnosis of MS and to look for findings that suggest...

There is approximately 90% concordance between the presence of oligoclonal bands in the CSF and an elevated kappa free light chain index.

According to the 2024 McDonald Criteria, the presence of either OCB or an elevated kappa free light chain index counts as positive CSF.

The MS immunological "signature" for MS is the presence of at least 2 unique CSF-specific oligoclonal bands (OCB), not seen in a parallel serum profile (though I prefer at least 3); a raised IgG Index, fewer than 50 lymphocytes, and a minimally elevated protein. If an established test is available f...