The cerebrospinal fluid in multiple sclerosis. Quantitative assessment of intrathecal immunoglobulin synthesis by empirical formulae

Intrathecal synthesis of IgG occurs in more than 90% of patients with clinically definite multiple sclerosis. The prevalence and significance of intrathecal synthesis of IgA and IgM are, however, less thoroughly characterized. We estimated intrathecal synthesis of IBG, IgA and IgM with various empirical formulae. The concentrations of albumin, IgG, IgA and IgM and the presence of IgG oligoclonal bands were determined in CSF and serum from 350 patients, including 97 with clinically definite multiple sclerosis. Intrathecal synthesis of IgG oligoclonal bands was detected in 95% of patients with multiple sclerosis (95% confidence interval 88-98%). The IgG-index, an extended IgG-index, and a hyperbolic Ige formula performed approximately equally in identifying patients with MS, but they were all inferior to the detection of IgG oligoclonal bands. In quantitative measurements, the extended immunoglobulin indices appeared to perform well; studies comparing the extended IgA- and IgM-indices to qualitative analyses (electrophoresis or isoelectric focusing) are, however, needed to confirm this. Detection of intrathecal synthesis of IgA of IgM was of little value in the diagnosis of multiple sclerosis.