Quantitative cerebrospinal fluid IgG measurements as a marker of disease activity in multiple sclerosis.

The value of various parameters of reporting quantitative cerebrospinal fluid (CSF) IgG levels to indicate disease activity in 34 patients with clinically definite multiple sclerosis was examined. IgG alone correlated significantly with increasing degree of disability and increasing number of clinical central nervous system lesions. There was also a trend toward higher mean IgG levels when the course was relapsing and progressive as opposed to progressive or relapsing. For the IgG index, the relationships were the inverse of that noted with IgG alone. IgG-albumin ratio and IgG synthetic rate did not correlate significantly with course, number of CNS lesions, or degree of disability, and there was no statistically significant relationship between any parameter of reporting quantitative CSF IgG and age, duration of disease, history of recent exacerbation, or area of first involvement in the nervous system. We conclude that although newer methods of reporting CSF IgG elevations in multiple sclerosis are more sensitive and some of them, more specific, in confirming a diagnosis than CSF IgG alone, this parameter remains the best marker of disease activity in individual patients.