N latex flc kappa kit

Laboratory analyses were performed in the Interdisciplinary CSF laboratory of the University Medicine Greifswald as described previously.^{7 (link),11 (link)}FLC-k in sera and CSF were measured by nephelometry with the N Latex FLC kappa kit (Siemens Healthcare Diagnostics Products GmbH, Marburg, Germany) according to the manufacturers protocol on the BN Prospec analyzer. CSF predilution was set to 1:1; serum predilution was set to 1:100. The lower limit of quantification was 0.034 mg/L and was given by the manufacturer (details are provided in table e-1, links.lww.com/NXI/A316).
The hyperbolic reference range and the amount of intrathecal synthesized FLC-k was calculated according to the formulas defined by Reiber et al.^{11 (link)}

Licensed laboratory technicians in the Clinical Neurochemistry Laboratory at Sahlgrenska University Hospital performed the biomarker analyses. Cerebrospinal fluid and serum albumin and immunoglobulin G (IgG) levels were analysed using the IGG-2 and ALBT2 reagent cassettes on a Cobas C module instrument (Roche). The CSF/serum albumin ratio was calculated as (CSF albumin [mg/L]/serum albumin [g/L]). Serum and CSF concentrations of kappa free light chain (KFLC) were measured using the N Latex FLC kappa kit, on an Atellica NEPH 630 instrument (Siemens), following the instructions by the manufacturers. The KFLC index was calculated using the equation ([CSF KFLC/serum KFLC]/[CSF albumin/serum albumin]). CSF neurofilament light (NfL) concentration was measured with a sandwich ELISA method (NF-light^® ELISA kit, UmanDiagnostics AB, Umeå, Sweden). Intra- and inter-assay coefficients of variation were below 10%. The LLOQ of the assay was 31 ng/L. Plasma NfL concentration was measured using the Simoa^® NF-light™ Advantage Kit on an HD-X Analyzer (Quanterix, Billerica, MA). The intra-assay and inter-assay coefficients of variation were below 10%.