Onward and upward While the scientific debate r

Onward and upward

While the scientific debate raged through November, the MAST pilot in Liverpool deployed more than 100,000 Innova tests, which identified about 1,000 positive cases. No results have been formally published, but preliminary data was buried in an appendix to the government’s new mass screening guidelines, which were released on Nov. 30. The report says Innova’s antigen test picked up just 5 of the 10 infections detected by PCR and “more than seven out of 10 cases with higher viral loads, who are likely to be the most infectious.”Nevertheless, Hancock has hailed MAST as a success and credits it with helping reduce the infection rate in the city to about 100 per 100,000; however, the region also implemented strict social-contact restrictions that would have significantly curbed infections anyway. So far, Innova has shipped 120 million–140 million tests to the UK, where they are being rolled out to 67 more towns and cities. The company is bidding for a new UK government contract, valued at £912 million.

This repeated testing catches all those little embers that could start local fires but instead get extinguished quickly.
Daniel B. Larremore, infectious disease modeler, University of Colorado Boulder
However, Daniel B. Larremore, an infectious disease modeler at the University of Colorado Boulder, believes the Innova test could help control infections. He and his colleagues have modeled the effectiveness of a rapid antigen test operating at a similar limit of detection and sensitivity as the Innova test; they found that the frequency of testing and how quickly the results are reported are far more important than sensitivity to ensure a successful screening program (Sci. Adv. 2020, DOI: 10.1126/sciadv.abd5393).

Their model simulated a population of 10,000 people and predicted how well an outbreak could be controlled by isolating positive cases after screening with one of two tests: a rapid antigen test that could detect viral loads equivalent to 100,000 RNA copies per milliliter and an RT-PCR test that can typically detect around 1,000 viral RNA copies per milliliter.

Although the antigen test was less sensitive than RT-PCR, it delivered results almost instantly, while RT-PCR took up to 2 days to process. The model predicted that giving people the antigen test every 3 days would reduce the overall infectiousness of the population by about 80%. “This repeated testing catches all those little embers that could start local fires but instead get extinguished quickly, ” Larremore says. In contrast, an RT-PCR test offered at the same frequency would reduce infectiousness by only about 50%.

“There’s been a big discussion among scientists about the validity of asymptomatic testing,” says Deenan Pillay, a virologist at University College London. “Personally, I support more aggressive screening, especially with younger populations, where a greater proportion of people are going to be asymptomatic.”

https://cen.acs.org/biological-chemistry/infe...ing/98/i48