A new examine raises vital doubts about whether or not at-home fast antigen assessments can detect the Omicron variant earlier than contaminated folks can transmit the virus to others.
The study looks at 30 people from settings together with Broadway theaters and workplaces in New York and San Francisco the place some employees weren’t solely being examined every day however had been, due to guidelines at their workplaces, receiving each the antigen assessments and a every day take a look at that used the polymerase chain response, or PCR, which is believed to be extra dependable.
On days 0 and 1 following a optimistic PCR take a look at, all the antigen assessments used produced false-negative outcomes, despite the fact that in 28 of the 30 circumstances, ranges of virus detected by the PCR take a look at had been excessive sufficient to contaminate different folks. In 4 circumstances, researchers had been capable of affirm that contaminated folks transmitted the virus to others through the interval earlier than that they had a optimistic outcome on the fast antigen take a look at.
“I feel that with each new variant that comes, scientists should query whether or not the issues that had been beforehand true are nonetheless true,” mentioned Blythe Adamson, the lead writer of the paper and the principal epidemiologist at Infectious Economics in New York. “This one has a special method it travels, a special mechanism of motion of signs, it has completely different home windows of transmission.”
Adamson, who can also be an worker of Flatiron Well being, a unit of Roche, mentioned that it was additionally doable there have been extra circumstances of transmission than the authors had been capable of affirm.
“It’s completely possible there have been many greater than 4 transmissions,” Adamson mentioned. “We named 4 as a result of there have been 4 that had been confirmed by contact tracing and epidemiology investigation. There have been possible many extra.”
The examine included each the Abbott BinaxNOW and Quidel QuickVue fast antigen assessments, each of that are approved by the Meals and Drug Administration.
The outcomes had been printed in a preprint, which means they haven’t but been reviewed by exterior researchers.
Different knowledge from the group point out that viral masses peaked in saliva one to 2 days earlier than they peaked in assessments taken from nasal swabs, including to proof that swabs taken from the mouth or throat could detect the SARS-CoV-2 that causes Covid higher than the nasal swabs used for a lot of PCR and antigen assessments.
“This group of specialists who’ve been doing sequential testing is elevating the uncomfortable chance that antigen testing is lacking folks that may infect others,” mentioned Harlan Krumholz, director of the Middle for Outcomes Analysis and Analysis at Yale. “They’re utilizing state-of-the-art strategies and sound epidemiologic approaches leveraging a well-designed occupational well being program.”
Whereas he was not concerned within the analysis, Krumholz is thanked in acknowledgements part of the paper.
Regardless of its small dimension, the ends in the examine are remarkably constant. Not a single fast antigen take a look at detected the virus till practically two days after the preliminary optimistic PCR outcome. Moreover, the circumstances of an infection from individuals who had acquired false damaging outcomes might increase alarm bells.
Nevertheless, the researchers emphasize, this doesn’t imply that fast antigen assessments are usually not helpful. The assessments additionally detected the virus in each case – it simply took longer than with PCR. So whereas the assessments could not work as an early warning, a optimistic take a look at outcome at dwelling does possible imply that the individual taking the take a look at has Covid-19.
Anne Wyllie, a researcher on the Yale College of Public Well being and a co-author on the paper, mentioned that the experiences she is seeing from most of the people on social media additionally increase her stage of concern.
“If most of the people is seeing this and reporting on it, , that is additionally loads of proof for me,” Wyllie mentioned. “Like they’re really seeing it. This can be a lot extra widespread than simply this one outbreak that we had been observing.”
Throughout the pandemic, Adamson and Infectious Economics turned consultants to many Broadway productions that had been making an attempt to maintain their staffs secure from Covid. The chance to audiences was comparatively simple to regulate, however forged and crew members labored in cramped quarters the place numerous security precautions, together with vaccination, masking, and using fast assessments had been all essential to hold folks secure.
She mentioned that as quickly as Omicron hit, there have been anecdotes about fast antigen assessments remaining damaging till days after the contaminated folks had already developed signs. She mentioned she began to really feel anxiousness about whether or not precautions to maintain forged members secure can be sufficient. Since then, quite a few Broadway exhibits, including “Waitress” and “Jagged Little Pill,” have introduced Covid-related closures.