Four formulas for calculating cerebrospinal fluid immunoglobulin G abnormalities in multiple sclerosis

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The authors used laser immunonephelometry to measure cerebrospinal fluid and serum immunoglobulin G and albumin in patients with multiple sclerosis and other neurological diseases known to cause increased cerebrospinal fluid immunoglobulin G. The Wilcoxon rank-sum test showed that for four commonly used formulas (Tourtellotte’s, Schuller’s, the immunoglobulin G index, and immunoglobulin G/albumin) the definite multiple sclerosis group had significantly higher values of these variables than did the normal group or the groups with possible multiple sclerosis, other neurological diseases, or nonimmunological other neurological diseases. McNemar’s test of symmetry showed that Tourtellotte’s formula was more sensitive than other formulas and that Schuller’s formula was slightly more specific than other formulas. Receiver operating characteristic curves showed that there was little difference among the formulas.



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