The new Fructosamine assay for the ARCHITECT cSystems instrument

Abstract

Detection of cerebrospinal fluid (CSF) specific oligoclonal bands (OCB) supports the diagnosis of multiple sclerosis (MS), but the method is technically demanding and gives only qualitative information. Kappa free light chains (KFLC) quantification could represent a convenient alternative. We evaluated the diagnostic accuracy of OCB and KFLC in our cohort to further estimate the gain in diagnostic performance when combining both of them.KFLC were measured in paired serum and CSF samples of 80 patients with MS and 50 patients with non-inflammatory neurological disorders. OCB were detected using an in-house alkaline phosphatase assay. Likelihood ratio (LR) was used to explore the benefit of the combined KFLC and OCB test.Sensitivity of KFLC index (≥5.3) and intrathecal KFLC fraction (≥10%) was 96% and 95% respectively, compared to 91% sensitivity of OCB assay. Specificity was 96% for intrathecal KFLC synthesis and 98% for OCB. Probability of MS in the absence of OCB was further reduced with concurrently normal KFLC index.Normal KFLC parameters allow confident exclusion of intrathecal inflammation, but probability of MS is greater with positive OCB. Use of KFLC as an adjunct test might be beneficial in specialized MS centers with larger pretest probability.