This yr, as they put together to let turkeys brine and pie crusts thaw, folks throughout the nation are ready for one thing additional: a coronavirus check they hope can clear them to mingle with family members.
As a result of a constructive check filters out individuals who ought to undoubtedly not be out with others, many individuals take into account a destructive coronavirus check to be a ticket to freely socialize with out precautions. However scientists and medical doctors say that is dangerously misguided.
The primary cause is that a check offers details about the extent of the virus on the time of the check. An individual could possibly be contaminated however not have sufficient virus for it to register but. Or, an individual might develop into contaminated within the hours or days after taking a check. Additionally, the exams would not have 100 % accuracy.
“If you happen to require all your friends to e mail you a destructive check consequence earlier than your Thanksgiving dinner, it is going to undoubtedly lower the danger of an outbreak — however not fully,” mentioned Dr. KJ Seung, chief of technique and coverage for the Covid response at Companions in Well being. But this can be a widespread misperception contact tracers hear when speaking to folks, he mentioned.
Laboratory exams that depend on a way referred to as polymerase chain response, or P.C.R., can detect the virus when it’s current even at very low ranges. Nevertheless it may take a few days to return outcomes, leaving time for somebody to be uncovered.
Antigen exams are quicker, cheaper and extra handy — they’ll ship leads to a matter of minutes — however are additionally extra liable to lacking the virus when it’s scarce. And that might give somebody a false sense of safety en path to Thanksgiving dinner, mentioned Paige Larkin, a medical microbiologist at NorthShore College HealthSystem in Chicago, the place she focuses on infectious illness diagnostics.
“A destructive result’s a snapshot in time,” Dr. Larkin mentioned. “It’s telling you that, at that actual second you’re examined, the virus was not detected. It doesn’t imply you’re not contaminated.”
In abstract, as Dr. Esther Choo, an emergency drugs doctor and a professor at Oregon Well being and Science College, put it: “Testing destructive principally adjustments nothing about conduct. It nonetheless means put on a masks, distance, keep away from indoors if you happen to can.”