Agarose electrophoresis and immunonephelometric quantitation of cerebrospinal fluid immunoglobulins: criteria for application in the diagnosis of neurologic disease.

The cerebrospinal fluid (CSF) IgG index, the CSF to serum albumin ratio, and electrophoresis on agarose gel of CSF and serum were evaluated retrospectively for their usefulness in the differential diagnosis of multiple sclerosis (MS). Standardized procedures were adopted for grading the intensity of oligoclonal banding and for the certainty of diagnosis of MS. One hundred and forty-nine patients were studied, including 23 with definite multiple sclerosis (MS), 12 with probable MS, 20 with possible MS, 20 with inflammatory neurologic disease, 65 with noninflammatory neurologic disease, and nine with no neurologic disease. The CSF IgG index and the CSF to serum albumin ratio were calculated from nephelometric measurements of serum and CSF IgG and albumin. The intensity of oligoclonal banding was graded relative to the density of the prealbumin band. Eighty-eight per cent of cases of definite MS had distinct oligoclonal bands, and an equal number had an elevated IgG index. These tests were not specific for MS, however, since 50% of cases of inflammatory neurologic disease and 5% of those with noninflammatory neurologic disease had an elevated IgG index. Similarly, 48% of cases with inflammatory disease and 25% with noninflammatory disease had oligoclonal bands. However, only patients with definite MS (21%) or possible MS (4%) had prominent oligoclonal bands whose density was greater than or equal to that of prealbumin, together with a CSF IgG index greater than 1.50. This combination of findings therefore may enhance the level of suspicion of MS. By contrast, an isolated increase in the CSF to serum albumin ratio may suggest a diagnosis other than MS.