Is it worth to report the presence of a single and additional band in the cerebrospinal fluid detected by isoelectrofocusing?

Despite the revisions of the Mac Donald criteria of multiple sclerosis (MS) in 2010, the cerebrospinal fluid (CSF) analysis by isoelectrofocusing (IEF) remains useful for atypical presentations of MS. The IEF is considered as positive when at least two or more additional bands are detected in the CSF by comparison with the patient's serum but sometimes, the IEF interpretation is more difficult. The goal of our study was to determine the significance when a single band in the CSF is detected by IEF. We conducted a retrospective study on 990 patients who underwent a lumbar puncture followed by a CSF analysis by IEF. Only 2% display such IEF profile (i.e. single and additional band in the CSF). A diagnosis of clinically isolated syndrome or MS was evidenced in 4 among those 21 patients. In conclusion, our data suggest that even if the presence of a single and additional band in the CSF is a rare situation, it should be mentioned to clinicians to not exclude the hypothesis of an inflammatory demyelinating disease of the central nervous system.