Samples were handled and biobanked according to international recommendations.38 Blood was sampled in the morning in fasting conditions, subsequently kept at room temperature for 15–30 min to allow clot formation, then refrigerated at 4°C, and finally centrifuged (2000 × g, 10 min) and stored at −80°C in 0.5‐ or 1‐mL aliquots in polypropylene vials within 4 h from sampling. sGFAP was measured with a commercial kit (catalog number, 102336) on the Simoa SR‐X instrument (Quanterix, Lexington, MA, USA). Samples were measured in duplicates, with coefficients of variation (CVs) <20%. All samples had sGFAP levels above the limit of detection (LOD) and lower limit of quantification (LLOQ), which were 0.26 and 1.37 pg/mL, respectively.
Simoa sr x
Manufactured by Quanterix
Sourced in United States
The Simoa SR-X is a high-sensitivity immunoassay platform developed by Quanterix. It is designed to detect and quantify low-abundance proteins and other analytes in biological samples with exceptional sensitivity and precision.
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Lab products found in correlation
5 protocols using simoa sr x
1
Biobanking and Quantification of sGFAP
2
Plasma NfL Measurement Protocol
3
Longitudinal Biomarkers in Relapsing-Remitting MS
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For pwPMS, the following variables were registered at baseline: date of birth, date of MS diagnosis, sex, baseline age and disease duration, current disease-modifying therapy (DMT), PRO measures, and date of completion.
For pwRMS, the same variables were recorded at baseline plus cerebrospinal fluid (CSF) neurofilament light chain protein (NFL) and chitinase3 like-1 (CHI3L1) levels, and CSF oligoclonal G and M bands (for Methods22 (link)). CSF biomarkers were available in 50 pwRMS (58.1%). During the 2-year study period and every three to six months, serum NFL – measured with SiMoA SR-X according to manufacturer’s instructions [Quanterix Corporation, Lexington, MA 02,421, USA]—EDSS, symbol digit modality test (SDMT)40 (link), 9-hole peg test (9-HPT)41 (link), and timed 25-foot walk test (T25-FW) were registered41 (link).
For pwRMS, the same variables were recorded at baseline plus cerebrospinal fluid (CSF) neurofilament light chain protein (NFL) and chitinase3 like-1 (CHI3L1) levels, and CSF oligoclonal G and M bands (for Methods22 (link)). CSF biomarkers were available in 50 pwRMS (58.1%). During the 2-year study period and every three to six months, serum NFL – measured with SiMoA SR-X according to manufacturer’s instructions [Quanterix Corporation, Lexington, MA 02,421, USA]—EDSS, symbol digit modality test (SDMT)40 (link), 9-hole peg test (9-HPT)41 (link), and timed 25-foot walk test (T25-FW) were registered41 (link).
4
Cerebrospinal Fluid Biomarkers in HIV
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Atraumatic needles were used for lumbar punctures (LPs). CSF was analyzed for cell count and several biomarkers. CSF total tau (t-tau), phosphorylated tau (p-tau), and β-amyloid 1–42 fragment (Aβ1-42) were measured by immunoenzymatic methods (Innotest, Fujirebio Europe, Belgium) with limits of detection (LoD), respectively, of 34, 15.6, and 65 pg/ml. Neopterin and S100-beta were measured through validated ELISA methods (DRG Diagnostics, Marnurg, Germany, and DIAMETRA Srl, Spello, Italy, respectively). Serum and CSF Neurofilament light chain (NFL) were evaluated with a new digital immunoassay, the Single Molecule Array technology (Simoa SR-X, Quanterix®, Billerica, USA) with the NF-light advantage® assay (LoD 0.038 pg/mL). Reference values were as follows: t-tau < 300 pg/mL (in patients aged 21–50), < 450 pg/mL (in patients aged 51–70), or < 500 pg/mL in older patients, p-tau (< 61 pg/mL), Aβ1-42 (> 500 pg/mL), neopterin (< 1.5 ng/mL) and S100-beta (< 380 pg/mL). CSF indexes of blood–brain barrier permeability (CSF to serum albumin ratio, or CSAR) were deemed normal when < 6.5 in patients aged < 40 or < 8 in patients > 40 years (20). HIV-RNA was quantified by the Roche Amplicor assay v2.0 (Hoffman-La Roche, Basel, Switzerland) with a lower limit of quantification of 20 copies/ml.
5
Serum NfL Biomarker Analysis Protocol
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Serum NfL was analyzed using the Quanterix Simoa SR-X platform. Samples were analyzed in duplicate and the CoV for each pair calculated as (standard deviation of duplicate values) divided by (mean of duplicate values) and expressed as a percentage. Mean(SD) CoV for NfL was 5.0 ± 4.6% (range 0.01–19%). Frozen serum aliquots were stored onsite at −80 °C and batch analyzed at end of study. Several serum aliquots from 11 participants were thawed and then refrozen during storage due to a freezer malfunction. These samples were included in NfL analysis because it is known to be robust to freeze–thaw cycles (Keshavan et al., 2018 ).
An attempt was made to analyze serum MIF and serum TNF-α changes, as peripheral markers for neuroinflammation. However, the results of serum MIF or TNF-α analyses were not interpretable due to preanalytical issues as follows and hence not presented in this paper. There was (a) false 3x elevation of serum MIF in visibly hemolyzed samples, presumably due to release of MIF from erythrocytes and without relation to treatment (data not shown) and (b) serum TNF-α levels were near lower limits of quantification (ELISA; electrochemoluminescence) and highly variable (coefficient of variance (CoV) 25–40%).
An attempt was made to analyze serum MIF and serum TNF-α changes, as peripheral markers for neuroinflammation. However, the results of serum MIF or TNF-α analyses were not interpretable due to preanalytical issues as follows and hence not presented in this paper. There was (a) false 3x elevation of serum MIF in visibly hemolyzed samples, presumably due to release of MIF from erythrocytes and without relation to treatment (data not shown) and (b) serum TNF-α levels were near lower limits of quantification (ELISA; electrochemoluminescence) and highly variable (coefficient of variance (CoV) 25–40%).
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