LAUSR

Our study aim was to evaluate the performance of the automated Sysmex HISCL® SARS-CoV-2 antigen assay against RT-PCR. We tested 277 remnant frozen nasopharyngeal swab samples, stored in universal transport medium (UTM), yielding a sensitivity of 94.9% against historical RT-PCR results with cycle threshold (Ct) <30, and a sensitivity of 76.7% for Ct<35, and specificity of 100% (all Ct values) confirming compatibility of UTM-diluted samples with the assay system. Thereafter, we prospectively collected 141 nasopharyngeal swab samples in UTM from healthcare workers and 1369 paired swabs (400 UTM; 969 dry) from individuals at a public health testing centre, with the first swab (UTM) reserved for RT-PCR, yielding a positivity rate of 4.6%. HISCL assay performance using UTM swabs was superior to dry swabs, with a sensitivity of 100% (95%CI 71.5-100%) at Ct<30 versus 92.3% (95%CI 81.5 - 97.9%), and a specificity of 99.3% (95%CI 98.1-99.89) against 83.3% (95%CI 80.7 - 85.6%). We conclude that this antigen assay is suitable for high throughput facilities where the primary indication for testing is to rule out infection with low RT-PCR Ct values (proxy for high viral loads) to curb viral spread. This article is protected by copyright. All rights reserved.