"Contagious tests"2 Oct 2020 12:54
https://www.theatlantic.com/health/archive/2020/08/how-to-test-every-american-for-covid-19-every-day/615217/
Informative and lengthy article published in The Atlantic.com ( August 2020).
(It should be noted that Avacta is targeting the "most infectious" persons with the development of its rapid Covid 19 antigen test . The company has used that terminology in recent RNS releases )
From the article,
Professor Mina (Harvard University)
"There is good evidence to infer that a high viral load, which is what antigen tests detect, is correlated with infectiousness. The more virus in your body, the more contagious you are........
In that light, paper antigen tests aren’t SARS-CoV-2 tests at all, not like PCR tests are. They are rapid, cheap COVID-19 contagiousness tests. That shift in thinking, Mina argues, should undergird a shift in our national strategy.....
Mina wants to coat the country in COVID-19 contagiousness tests. To understand the scale of his vision, start with the closest American analogue, the ubiquitous, paper-based, inexpensive at-home pregnancy test. Americans use 20 million of those each year. "
An interesting comment in the article from the CEO of "e25 bio" Bobby Brooke Herrera .This is the start up company which has only 12 employees in Cambridge USA and has now abandoned development of its rapid antigen Covid 19 saliva test . It appears e25 bio struggled to reach the minimum FDA sensitivity requirement of 80% for rapid antigen tests. Shame they don't have affimers to use !
“The FDA, early on in the outbreak, said we had to follow a rubric of 80 percent sensitivity compared to PCR. How they got that number, I’m uncertain, but my best guess is it came from influenza epidemics in the past,” Herrera said.
This requirement has made antigen tests worse, Herrera argues, because it causes manufacturers to prioritize sensitivity at the cost of speed or convenience. It’s why other antigen tests use readers, or centrifuges, or look for nucleocapsid, he contends. By slightly weakening those guidelines, to 60 or 70 percent sensitivity, the FDA could let cheaper at-home tests come to market. The models that e25 uses show that even an at-home test that caught 50 percent of positives and 90 percent of negatives could detect outbreaks and reduce COVID-19 transmission."
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