Evaluation of formulae for CSF IgG synthesis using data obtained from two methods: Importance of receiver operator characteristic curve analysis

Abstract

Aims - To determine (CSF) IgG synthesis formulae using data obtained from two quantitation methods. Methods - Receiver operator characteristic (ROC) analysis and decision index plots were used to compare a rate nephelometric (RN) and a rocket immunoelectrophoretic (RIEP) method for quantitating albumin and IgG for use in CSF IgG synthesis formulae. Further analysis was used to determine the most clinically accurate of these formulae for a diagnosis of multiple sclerosis with regard to technical accuracy and cost effectiveness. Results - Values for albumin and IgG determined by RN gave better sensitivities and specificities than the RIEP method when applied to all three formulae; however, when the 95% confidence Limits were considered, the difference was not significant. Using the RN method with an agreed 'rule in' threshold value of 90% specificity, the IgG index gave the best clinical performance. Conclusion - ROC curve analysis and decision index plots provide valuable tools in assessing and comparing the clinical performance of new and existing laboratory assays.