The CerebrospinalFluidImmunoglobulinG Indexas a DiagnosticAid in

Having determined immunoglobulin G (lgG) and albumin concentrations in 1100 cerebrospinal fluid and serum samples, we calculated the IgG index. Likelihood ratios for multiple sclerosis were calculated by using a training set consisting of 100 patients with definite multiple sclerosis and one consisting of 97 patientssufferingfrom diseases from which multiple sclerosis must be differentiated. Predictive values for multiple sclerosis, given different values for the IgG index, are given in a graphical repre-sentation of Bayes ’ theorem. We conclude that this ap-proach Increases the diagnostic usefulness of the lgG index for the diagnosis of multiple sclerosis. AddItIonal Keyphrases: Ilkellhood ratio. predictivevalue Bayes ’ theorem. interpretation of laboratoty data The cerebrospinal fluid (CSF) IgG index has been advo