Impact of intrathecal IgG synthesis on neurological disability in patients with multiple sclerosis

Background: The association between routine laboratory findings, including cerebrospinal fluid biomarkers, and neurological outcomes in patients with multiple sclerosis (MS) has not been fully elucidated. In this study, we evaluated blood and cerebrospinal fluid (CSF) analysis results at diagnosis and before treatment in patients with MS and assessed their correlations with neurological outcomes. Materials and methods: In this study, 38 consecutive patients with MS (36 with relapsing-remitting MS and 2 with primary progressive MS) were recruited. Before treatment, all patients underwent routine CSF analysis at the time of diagnosis, including evaluation of albumin and immunoglobulin G (IgG) levels. The association between laboratory data and neurological outcomes was comprehensively evaluated. Subsequent neurological outcome was assessed by using the Expanded Disability Status Scale (EDSS) score at 1 year and 5 years after diagnosis and relapse frequency in the first year and in the first 5 years. Results: The IgG level in the CSF (rho = 0.46, p = 0.004), oligoclonal band count (rho = 0.61, p = 0.006), ratio of IgG and total protein in CSF (rho = 0.59, p < 0.0001), and ratio of IgG and albumin in CSF (rho = 0.67, p < 0.0001) showed moderate to strong correlations with the subsequent EDSS score 1 year after diagnosis. These variables still showed significant correlations with EDSS 5 years later. Albumin and lactate dehydrogenase levels in CSF did not correlate with the subsequent EDSS score. Relapse frequency did not correlate with any of the studied serum and CSF biomarkers. Conclusion: IgG levels in CSF at MS diagnosis are significantly correlated with the level of neurological disability independent of the relapse frequency. Markers of intrathecal IgG synthesis, such as the IgG index, are useful in estimating the present and subsequent clinical severity in patients with MS.