Simoa nf light advantage assay

Blood samples were not systematically collected as part of the original study protocol, but 133 of the 166 participants with longitudinal follow‐up had at least one plasma or serum samples available for analysis. A mean of 1.5 samples (range 1–3) were available for each participant in the study, with sample availability well balanced between those defined as having a good or poor outcome (Table 1). Most samples analyzed were plasma. As serum and plasma NfL are strongly correlated in RRMS (r = 0.89–0.96), and the proportion of plasma and serum samples were well balanced between the two outcome groups (Table 1), we included all plasma and serum samples in the analysis without adjustment (Hendricks et al., 2019 (link), Sejbaek et al., 2019 (link)).
Samples were collected at the time of clinical assessments and stored at −80°C until the time of analysis. All samples were analyzed in duplicate using the Quanterix Simoa NF‐light advantage assay on a HD‐1 Analyser (Quanterix, Billerica, MA, USA). Recent reports have highlighted the benefits of analyzing NfL as age‐ and body mass index (BMI)‐adjusted Z‐scores (Benkert et al., 2022 (link)). Since access to the required control and BMI data were not available for this historical cohort, we analyzed NfL without adjustment, but included age as a covariate in all multivariable analyses.