By Dennis Thompson
MONDAY, Aug. 31, 2020 (HealthDay Information) — The brand new speedy COVID-19 take a look at permitted final week might be not probably the most dependable choice for figuring out whether or not somebody is contaminated.
Nevertheless it’s low-cost and it is quick, and if used appropriately, it could possibly be the idea of a screening technique to maintain Individuals protected as they return to high school and work, infectious illness consultants say.
The BinaxNOW COVID-19 Ag Card produced by Abbott Laboratories is an antigen take a look at, a kind of scan that appears for particular structural proteins of the coronavirus that kind throughout an infection. The take a look at will produce outcomes inside quarter-hour and price $5, Abbott says.
Antigen checks are infamous for producing many false positives, indicating that individuals are contaminated once they actually aren’t, mentioned Dr. Gary Procop, medical director and co-chair of the Enterprise Laboratory Stewardship Committee on the Cleveland Clinic in Ohio.
And he mentioned that is completely effective if the take a look at is used appropriately, as a screening instrument to verify people contaminated with SARS-CoV-2 do not make it right into a crowded faculty or a basketball court docket or an meeting line.
“Everytime you do screening checks, you really need a number of false positives since you wish to seize everyone with illness,” Procop mentioned.
The secret is to make the antigen take a look at the primary in a two-step screening course of, he mentioned.
Everybody who checks constructive ought to then obtain a confirmatory PCR take a look at — a slower, extra complicated and extra correct kind of molecular scan that appears for the genetic materials of the brand new coronavirus, Procop mentioned.
“Lots of people just like the antigen take a look at as an preliminary display screen, as a result of it is cheap and it is fast, and you’ll get people who find themselves blazing constructive who you would not wish to sit subsequent to on a airplane,” Procop mentioned. “However you have to observe that up with a PCR take a look at, to weed out false positives.”
Abbott’s take a look at is promising sufficient that the White Home struck a cope with the corporate to buy 150 million take a look at playing cards for $760 million, basically shopping for out this 12 months’s product run, in line with Barron’s.
The deal got here someday after Abbott introduced U.S. Meals and Drug Administration approval of the take a look at for emergency use. The take a look at can solely be administered by a medical skilled, and isn’t permitted for residence use.
The take a look at appears one thing like a greeting card. A health care provider or nurse drips a take a look at answer right into a small properly within the card, after which slides a nasal swab pattern into the chemical. The highest a part of the cardboard is closed, and inside quarter-hour a consequence will seem — one line for a detrimental take a look at, two for a constructive.
Abbott says scientific research involving sufferers examined inside within the first seven days of symptom onset confirmed that BinaxNOW has a sensitivity of 97% and a specificity of greater than 98%. Meaning solely 3 in 100 checks will produce a false constructive, and fewer than 2 in 100 checks will return a false detrimental.
Antigen checks generally are typically much less delicate, as little as 70% relying on the take a look at, mentioned Dr. Amesh Adalja, a senior scholar with the Johns Hopkins Middle for Well being Safety in Baltimore.
However antigen checks are also extremely particular, hardly ever producing a false detrimental consequence, he mentioned.
Given all this, low-cost and quick antigen checks must be ok “to be geared towards the query, are you contagious or are you not, for asymptomatic people,” Adalja mentioned.
“You won’t want a take a look at as delicate because the PCR whenever you’re screening asymptomatic people like at a college, for instance, or a sports activities group,” he mentioned.
Then again, PCR checks are way more correct.
“That is how we diagnose acute an infection,” Adalja mentioned. “It is a very delicate take a look at. It picks up very low ranges of the virus’ genetic materials. Individuals will be constructive for this take a look at lengthy after they’re recovered and misplaced their contagiousness.”
However as a result of PCR samples should go to a lab, the checks require much more processing time, Adalja mentioned. Additionally they require chemical compounds which have typically been in brief provide, additional delaying outcomes.
Procop mentioned he depends on PCR checks when testing clearly sick folks in essential conditions, equivalent to previous to admission to the intensive care unit.
Because the antigen take a look at may miss a COVID-19 an infection, “I might by no means use these if I used to be going to place somebody in an ICU primarily based on that, as a result of I’ve acquired an actual danger of infecting different sufferers and infecting well being care employees,” Procop mentioned. “I am unable to afford to be improper in that setting.”
However Procop mentioned the antigen take a look at could possibly be an excellent screening instrument when adopted up with PCR take a look at. He likened the technique to early HIV tests, the place a fast screening immunoassay that was constructive was adopted by a extra in-depth laboratory take a look at to verify the analysis.
He hopes that the brand new take a look at heralds one thing the USA has been lacking since pandemic started — a nationwide testing technique to detect COVID-19 circumstances and defend the populace.
“We all know how you can display screen populations. We do a display screen take a look at after which we observe it up with a confirmatory take a look at. Why are we not doing that now?” Procop mentioned, including that the pandemic has made folks “loopy.”
“They’ve simply deserted every little thing we have recognized for the final 100 years and determined to re-create it from scratch, and guess what they’re discovering out? The tried-and-true is the tried-and-true,” Procop mentioned.