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October 08, 2021
As it was with the previous administration, widespread distribution and use of rapid, self-administered COVID-19 antigen tests are a crucial element of the Biden pandemic response strategy. But the science underlying the efficacy of direct antigen rapid tests for detecting SARS-CoV-2 remains a work in progress. It is universally recognized that rapid antigen tests are not as accurate as real-time quantitative polymerase chain reaction (qRT-PCR) tests detecting viral molecular RNA. The key question is whether the tests are reliable enough for use in asymptomatic screening and preventing the spread of the virus in work and public social settings. An important new study published by the JAMA suggests that they are.
The Stakes Are High
What rapid antigen tests lack in accuracy they make up for in cost, speed, ease of use and scalability. Unlike qRT-PCR tests, they can be performed at the point of care without the use of complex equipment and RNA separation processes. As a result, they are seen as integral for use in surveillance and screening asymptomatic populations in workplaces, schools, travel points and other social settings. Adding to their efficacy is that these tests are now becoming increasingly available for over-the-counter sale and at-home use.
Rapid, at-home antigen tests figure prominently in the new action plan that the President outlined in early September. Specifically, the Biden Path Out of the Pandemic plan, proposes measures to promote widespread use of rapid COVID-19 testing nationwide. Among other things, the plan calls for stepping up test production via government purchase of nearly $2 billion worth of rapid point-of-care and over-the-counter, at-home tests from multiple manufacturers. The administration will make the roughly 280 million tests available to long-term care facilities, community testing sites and programs supporting vulnerable populations, as well as for creating testing stockpiles for the future.
The plan also aims to make tests more affordable and accessible to consumers, including via arrangements with major retailers like Walmart, Amazon and Kroger for sale of at-home rapid COVID-19 tests to consumers at cost over the next three months, resulting in price reductions of up to 35 percent. In addition, the administration plans to send 25 million free at-home rapid COVID-19 tests to 1,400 community health centers and hundreds of food banks across the country.
The JAMA Study
The underlying premise behind all of this is that rapid antigen tests can be trusted to provide the necessary accuracy to get the job done. Although the early studies are encouraging, the scientific reliability of SARS-CoV-2 antigen tests remains largely unproven. In this context, the new study, which was published in JAMA Open Network on August 27, is of potentially great significance.
Until now, nobody has done a longitudinal comparison between antigen tests performed at home and qRT-PCR, at least to the knowledge of the study authors. So, the authors broke new ground by comparing high-frequency testing using inexpensive, at-home, semiquantitative, direct antigen rapid tests (DARTs) to qRT-PCR on self-collected nasal specimens. The study included 257 individuals who self-collected a total of 2,951 nasal swab samples for both DART and real-time PCR testing.
Study participants were affiliated with three coworking laboratories in Cambridge and Boston, Massachusetts, a region which at the time of the study had a COVID-19 prevalence of between less than 1 percent and 8 percent.
Nasal swab specimens were collected twice weekly over a six-month period. DART testing was performed at home, while real-time PCR testing was conducted at a laboratory. The researchers collected symptom information contemporaneously.
The Study Results
The findings were quite encouraging for advocates of rapid, at-home SARS-CoV-2 antigen tests. The researchers found the sensitively of DART within zero to 12 days of symptom onset to be 78.9 percent, with a specificity of 97.1 percent. The duration of SARS-CoV-2 nucleocapsid and RNA detection for individual infections ranged from one to 12 days, with peak levels observed between two and six days of symptoms The sensitivity of DART was calculated for each day. DART sensitivity was 96.3 percent within days zero to three of symptom onset.
Significantly, DART performed twice weekly detected the infections of all 15 of the study participants that developed COVID-19. Among these 15 participants:
Eleven tested positive for COVID-19 on Day One or Day Two;
One was presymptomatic on the day of the initial DART positive result;
One’s SARS-CoV-2 infection was detected via real-time PCR a day before DART; and
One’s infection was detected by DART detected a day before real-time PCR testing.
Takeaway
The study’s findings suggest that twice-weekly DART testing can allow coworking sites to safely operate during the SARS-CoV-2 pandemic. Most of the positive participants reported that they did not recognize symptoms of COVID-19 until they received a positive result, the study authors noted. Thus, relying on symptom self-reporting can result in missed or delayed detection, allowing infected individuals to transmit the virus unknowingly. “Frequent at-home testing with DART allows infected individuals to be identified and quarantined immediately … [preventing] viral transmission in in-person work environments or other social settings.”
The study also suggests that despite having less sensitivity than PCR-tests, serial use of rapid antigen testing can still be effective in containing the spread of SARS-CoV-2. “Lockdowns could be avoided completely with a combination of vaccine mandates and high-frequency antigen testing protocols implemented for all in-person activities,” according to a study co-author.
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This article originally appeared in G2 Intelligence, Diagnostic Testing & Emerging Technologies, October 2021.
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