CSF biology and the diagnosis of multiple sclerosis

Through our experience, we have analyzed the value of immunological exploration, namely the calculation of the IgG index and isoelectrofocalization (IEF) in the detection of IgG IS for the diagnosis of multiple sclerosis (MS), a chronic inflammatory demyelinating disease of the central nervous system (CNS). To this end, we conducted a study involving 223 patients with suspected MS for whom a CSF immunoassay was requested. There were 2 groups of patients: 'MS' (n=54) and 'non-MS' (n=96). The IgG index was ≥ 0.7 in 43/53 of 'MS' patients and 15/94 of 'non-MS' patients. With regard to IEF, this technique showed a profile 2 or 3 (oligoclonal bands (BOC)+) in 51/54 'MS' cases. In 'non-MS' patients, IEF showed a profile 1 or 4 in 75 cases, and a profile (BOC+) in 21 cases. Sensitivity and specificity for the diagnosis of MS were 81%-84% for the IgG index and 94%-81% for the IEF, respectively. In conclusion, our results showed that IEF in CSF is the most sensitive test for detecting IgG IS and constitutes the 'Gold standard' in the biological exploration of MS.