Cobas e801 analyzer

TRAb (Elecsys Anti-TRAb v2, Roche Diagnostics; reference range, <2.0 IU/L), TgAb (Elecsys Anti-Tg, Roche Diagnostics; reference range, <28.0 IU/mL), and TPOAb (Elecsys Anti-TPO, Roche Diagnostics; reference range, <16.0 IU/mL) were measured on a Roche Cobas e801 analyzer (Roche Diagnostics) according to the manufacturer’s instructions. TSH (Elecsys TSH v2, Roche Diagnostics; reference range, 0.500-5.000 μIU/mL), free T4 (FT4, Elecsys FT4III, Roche Diagnostics; reference range, 0.90-1.7 ng/dL), and free T3 (FT3, Elecsys FT3III, Roche Diagnostics; reference range, 2.30-4.00 pg/mL) were measured on a Roche Cobas e801 analyzer (Roche Diagnostics) according to the manufacturer’s instructions. Increases of TRAb, TSH, FT4, and FT3 from baseline to 4 weeks after the third dose were defined as ΔTRAb, ΔTSH, ΔFT4, and ΔFT3, respectively, which were calculated as:
(value at 4 weeks after the third dose) - (value at baseline).
Increases of TgAb and TPOAb from 32 weeks after the second dose (pre-third dose) to 4 weeks after the third dose (post-third dose) were also defined as ΔTgAb and ΔTPOAb, respectively, and calculated as:
(vales at 4 weeks after the third dose) - (values at 32 weeks after the second dose).
Responders to increase in TRAb were defined as the subjects who exhibited increase in TRAb in a time dependent manner and had TRAb >1.2 IU/L at 4 weeks after the third dose.

Antibody against SARS-CoV-2 was measured by Elecsys Anti-SARS-CoV-2 Electrochemiluminescence Assay (Roche Diagnostics, Rotkreuz, Switzerland) using a fully automated Cobas e801 Analyzer (Roche Diagnostics) according to the manufacturer’s instructions. The assay uses a recombinant protein representing the nucleocapsid (N) antigen in a double-antigen sandwich assay format and detects total antibodies, including IgG. We decided to identify antibodies against N antigen because there was no information about the mutation on Spike gene of each infected SARS-CoV-2. Results are provided as numeric cutoff index (COI) values and are finally reported as positive (COI ≥ 1) or negative (COI < 1).

The Elecsys^® Anti-SARS-CoV-2 ECLIA assay (Roche Diagnostics AG, Rotkreuz, Switzerland) performed on the cobas e 801 analyzer (Roche Diagnostics) was used. This is a high-throughput assay with an estimated TAT of 20 min per sample. The assay is CE marked and at the beginning of May 2020, received the Food and Drug Administration's EUA. Results [in cut-off index (COI)] are determined automatically by the analyzer's software that compares the electrochemiluminescence signal obtained from the reaction product of the serum/plasma sample with the signal of the cut-off value previously obtained by calibration. The cut-off value for reactivity (positivity) is equal to 1.0 COI. The assay uses a recombinant protein representing the nucleocapsid antigen, and its format favors the preferential detection of late, mature, and high affinity antibodies. Therefore, despite that this assay detects all classes of immunoglobulin (IgA, IgM, and IgG), it detects predominantly IgG (10 (link)).