Diagnostic values of IgG-albumin index and agarose gel electrophoresis in neurologic diseases.

Sixty cerebrospinal fluids (CSFs) with paired serum samples from a variety of patients with neurologic diseases were studied using rate nephelometry to measure IgG-albumin index, and also agarose gel electrophoresis (EP) with protein blotting technique to characterize discrete IgG bands. The patients included: A) 16 cases of multiple sclerosis (MS); B) 23 cases of inflammatory diseases of the central nervous system (CNS); C) 21 cases of other non-inflammatory neurologic disorders. The average IgG-albumin index was 0.65 +/- 0.25 in Group A, 1.10 +/- 0.78 in B, and 0.50 +/- 0.12 in C. If 0.72 is taken as the upper normal limit, an increased index was found in 31%, 43% and 5% of Groups A, B and C, respectively. Discrete IgG bands were detected in 69%, 9% and 5% of Groups A, B and C, respectively. Gamma globulin bands were not always IgG, and true oligoclonal myeloma proteins were not encountered. It is concluded that both IgG-albumin index measurement and agarose gel EP are useful for diagnostic differentiation in neurologic diseases: the former, for inflammatory diseases of CNS; and the latter, for MS.