Assessment of twenty-two SARS-CoV-2 rapid antigen tests against SARS-CoV-2: A laboratory evaluation study

BackgroundRapid antigen testing is widely used as a way of scaling up population-level testing. To better inform antigen test deployment in Australia, we evaluated 22 commercially available antigen tests against the currently circulating delta variant, including an assessment of culture infectivity. MethodsAnalytical sensitivity was evaluated against SARS-CoV-2 B.1.617.2 (Delta), reported as TCID50/mL, cycle threshold (Ct) and viral load (RNA copies/mL). Specificity was assessed against non-SARS-CoV-2 viruses. Clinical sensitivity and correlation with cell culture infectivity was assessed using the Abbott PanBio COVID-19 Ag test. ResultsNineteen kits consistently detected SARS-CoV-2 antigen equivalent to 1.3 x 106 copies/mL (5.8 x 103 TCID50 /mL). Specificity for all kits was 100%. Compared to RT-PCR the Abbott PanBio COVID-19 Ag test was 52.6% (95% CI, 41.6% to 63.3%) concordant, with a 50% detection probability for infectious cell culture at 5.9 log10 RNA copies/mL (95% CI, 5.3 to 6.5 log10 copies/mL). Antigen test concordance was 97.6% (95% CI, 86.3% to 100.0%) compared to cell culture positivity. ConclusionsAntigen test positivity correlated with positive viral culture, suggesting antigen test results may determine SARS-CoV-2 transmission risk. Analytical sensitivity varied considerably between kits highlighting the need for ongoing systematic post-market evaluation to inform test selection and deployment.

Liquid chalk is an antiseptic against SARS-CoV-2 and influenza A respiratory viruses

The COVID-19 pandemic has impacted and enforced significant restrictions within our societies, including the attendance of the public and professional athletes in gyms. Liquid chalk is a commonly used accessories in gyms and is comprised of magnesium carbonate and alcohol that quickly evaporates on the hands to leave a layer of dry chalk. We investigated whether liquid chalk is an antiseptic against highly pathogenic human viruses including, SARS-CoV-2, influenza virus and noroviruses. Chalk was applied before or after virus inoculum and recovery of infectious virus was determined to mimic the use in the gym. We observed that addition of chalk before or after virus contact lead to a significant reduction on recovery of infectious SARS-CoV-2 and influenza but had little impact on norovirus. These observations suggest that the use and application of liquid chalk can be an effective and suitable antiseptic for major sporting events, such as the Olympic Games.