On cerebrospinal fluid immunoglobulin-G (IgG) quotients in multiple sclerosis and other diseases. A review and a new formula to estimate the amount of IgG synthesized per day by the central nervous system.

[ have been asked numerous times why the cerebrospinal fluid (CSF) immunoglobulin-G (IgG) content has to be expressed as a percentage of the CSF total protein to be discriminative for multiple sclerosis (MS). From a historical standpoint, KABAT et al. (1950) found that the absolute value of CSF IgG (mg IgG/100 ml CSF) was elevated virtually every time when CSF total protein was significantly increased no matter which disease caused it; however, they discovered when the results were expressed as a ratio of the total protein, there emerged a pattern which discriminated MS from most other diseases. Eighty per cent of patients with MS had an elevated lgG value (IgG/total protein in ~) > 13 ~ (mean + 2 standard deviations, P= 0.05). In subsequent reports by the same group, YAHR et al. (1954) and HARTER et al. (1962) found 67 and 73~ of patients with MS and neurosyphilis, respectively, had an elevated IgG value; whereas, only 5.5~ of 7225 patients who had a neurological disease other than a demyelinating disorder (MS, diffuse sclerosis, acute disseminated encephalomyelitis, and neuromyelitis optica) and neurosyphilis had an elevated value. It is not the purpose of this account to review in detail the incidence of abnormally elevated y-globulin quantitatively determined in CSF from MS patients reported by various investigators; TOURTELLOTTE (1970) has recently done this. In general the multitude of reports utilizing very different methods have confirmed the results presented by KASAT and his colleagues mentioned above obtained with the reliable and valid immunochemical method of KABAT et al. (1948). The quotients or ratios to be discussed are the following: IgG concentration expressed as a percentage of the total protein concentration; IgG concentration expressed as a percentage of the albumin concentration; igG concentration expressed