Simoa sr x instrument

EDTA plasma samples were collected, aliquoted, and stored at −80°C according to standard procedures. CSF samples were obtained by LP following a standard procedure, centrifuged in case of blood contamination, divided into aliquots, and stored in polypropylene tubes at −80°C until analysis.
Both cNfL and pNfL concentrations, in the entire sample cohort, were determined with the Single molecule array (Simoa) technology on a Simoa SR-X instrument (Quanterix, Billerica, MA, United States) using the commercially available NF-light advantage kit (Quanterix). The mean intra- and inter-assay coefficients of variation (CVs) were below 15% for both cNfL and pNfL.

After thawing, serum samples were centrifuged at 10,000 g for 10 min at + 4 °C to eliminate any debris. The serum NF-L concentration was measured, as for other cohorts previously evaluated by others research groups^{19 (link),35 (link),36 (link)}, using the commercially available Single Molecule Array NF-Light immunoassay Advantage kit; the GFAP Discovery kit was used for the GFAP determination. The biomarkers assays were performed using the Simoa SR-X instrument (Quanterix, Lexington, MA). The serum samples were diluted four-fold as suggested by the kit data sheet; calibrators (A-H) and quality controls were used to assess the concentration of the reference analytes. The limit of detection for the Simoa NFL assay was 0.0552 pg/ml and the lower limit of quantification was 0.316 pg/ml when compensated for a four-fold sample dilution; the limit of detection for the Simoa GFAP assay was 0.26 pg/ml and the lower limit of quantification was 1.37 pg/ml when compensated for a four-fold sample dilution. Samples were analyzed in duplicate, and the CV for the samples was below 20%. The researchers who performed the NF-L and GFAP assays had no information related to the clinical data. Blood samples from six HC stored in the IRCCS SYNLAB SDN Biobank were extracted and processed in the same manner.