Pre-analytical considerations in the development of a prototype SARS-CoV-2 antigen ARCHITECT automated immunoassay.

Abstract

To evaluate pre-analytical challenges related to high-volume central laboratory SARS-CoV-2 antigen testing with a prototype qualitative SARS-CoV-2 antigen immunoassay run on the automated Abbott ARCHITECT instrument. Contrived positive and negative specimens and de-identified nasal and nasopharyngeal specimens in transport media were used to evaluate specimen and reagent on-board stability, assay analytical performance and interference, and clinical performance. TCID50/mL values were similar for specimens in various transport media. Inactivated positive clinical specimens and viral lysate (USA-WA1/2020) were positive on the prototype immunoassay. Within-laboratory imprecision was≤0.10 SD (<1.00S/C) with a≤10% CV (≥1.00S/C). Assay reagents were stable on board the instrument for 14days. No high-dose hook effect was observed with a SARS-CoV-2 stock of Ct 13.0 (RLU>1.0×106). No interference was observed from mucin, whole blood, 12 drugs, and more than 20 cross-reactants. While specimen stability was limited at room temperature for specimens with or without viral inactivation, a single freeze/thaw cycle or long-term storage (>30days) at-20°C did not adversely impact specimen stability or assay performance. Specificity of the prototype SARS-CoV-2 antigen immunoassay was≥98.5% and sensitivity was≥89.5% across two ARCHITECT instruments. Assay sensitivity was inversely correlated with Ct and was similar to that reported for the Roche Elecsys® SARS-CoV-2 Ag immunoassay. The prototype SARS-CoV-2 antigen ARCHITECT immunoassay is sensitive and specific for detection of SARS-CoV-2 in nasal and nasopharyngeal specimens. Endogenous proteases in mucus may degrade the target antigen, which limits specimen storage and transport times and complicates assay workflow.