Quantification of Neurofilament Light in CSF and Serum

All measurements were performed by board-certified laboratory technicians in the Clinical Neurochemistry Laboratory at the Sahlgrenska University Hospital, i.e., by laboratory technicians who are licensed to perform clinical laboratory measurements by the National Board of Health and Welfare, a government agency in Sweden under the Ministry of Health and Social Affairs.
The concentration of NFL in CSF was measured with a sensitive sandwich ELISA method (NF-light ELISA kit; UmanDiagnostics AB, Umeå, Sweden) according to the ELISA kit instructions. The lower limit of quantification (LLoQ) of the assay was 31 ng/L. The intra-assay and interassay coefficients of variation were <10%.
The concentration of NFL in serum was determined with the NF-light assay, which was adapted for the Simoa platform with a Homebrew Kit (Quanterix Corp, Boston, MA). The LLoQ, which was determined by the blank mean signal at 610 SD, was 1.95 ng/L. All samples were measured in duplicate and were well above the LLoQ. The intra-assay and interassay coefficients of variation were <10%. The method is described in detail elsewhere.^{26 (link)}