By Annie Vainshtein
Rapid at-home antigen tests have become convenient tools for people hoping to quickly determine whether their cold symptoms are COVID-19.
But the tests, which are not as accurate as PCR lab tests but return results in far less time, can be hard to find in the Bay Area.
The two at-home tests approved by the Food and Drug Administration are Abbott Laboratories’ BinaxNow and Ellume’s COVID-19 home test. But at least in the Bay Area, it’s challenging to find a drugstore that isn’t sold out of BinaxNow, though Ellume is far easier to get.
Calls to numerous Bay Area drug stores — including CVS and Walgreens — found that many were sold out of Binax-Now but had Ellume kits available. Store employees said that supply was variable depending on the day. Online, too, many retailers — including Walgreens and Walmart — appear to be out of stock of BinaxNow. Even if you are able to place an online order, the tests may not be shipped immediately due to the high demand.
BinaxNow is cheaper than Ellume, but it’s still a significant cost. The product, made by Abbott Laboratories, comes in a two-test kit and is sold for around $23.99. Ellume has only one test swab and is sold in most places for $38.99.
“We typically don’t recommend Ellume because it’s more expensive,” said Nam Tran, a professor of pathology and laboratory medicine at UC Davis and a member of California’s COVID-19 Testing Task Force, who noted that in Davis, BinaxNow is virtually nowhere to be found.
President Biden said on Thursday that his administration would use federal law to ramp up production of rapid home tests, and also ensure that retailers including Walmart, Amazon and Kroger sell test kits “at cost” starting most likely next week. “At cost” means that the seller would not make profits, but it was not immediately clear what the new price would be.
BinaxNow and Ellume are the same in terms of how they collect samples, according to UCSF infectious disease expert Peter-Chin Hong.
Both are “better at detecting people with symptoms rather than people without symptoms,” he said.
Antigen tests, which detect proteins from the coronavirus, are less accurate than polymerase chain reaction or PCR tests, which examine small amounts of the virus’ genetic material, said Chin-Hong.
“The (antigen test) is kind of a coarse instrument,” said Chin-Hong. “It’s maybe like a child in a field looking for a helium balloon, and the balloon has to be huge and bright for the child who is the instrument, but if there are balloons that are deflated and small, the antigen won’t pick it up.”
The PCR test, by contrast, is more like a key that fits into a lock, he said.
Overall, experts say, people should use antigen tests about three to five days after exposure to the coronavirus, and use a PCR test — often required by schools or other workplaces — for added clarity. The two BinaxNow testing kits are meant to be used 36 hours apart, for accuracy in case a person gets a false negative. Test results are available in 15 minutes.
Ellume can take a bit longer, with some estimates of up to 45 minutes. To use it, you have to download an app and answer a number of questions.
As for the choice between BinaxNow and Ellume, Tran said, “Go with the one that is available, easy to use, and that you can afford.”
John Koval, media spokesperson for Abbott Laboratories, said that the company is seeing “unprecedented demand as case rates rise” and has been been scaling up manufacturing.
However, the company’s production was hobbled after it laid off hundreds of workers at two manufacturing sites and destroyed millions of test cards earlier this year, believing that demand had dwindled, according to the New York Times.
Ellume, with its app component, may not be the most intuitive test kit for the technologically unsavvy — but it offers an electronic receipt for the test that can be shown to employers if needed.
But the biggest benefit of the test is that it can be used for international travel for people coming back into the U.S — but you have to take it under video observation by a proctor. Abbott also has a BinaxNow Home Test — versus the Self Test — that is approved for international travel, but it’s not the one that’s available over the counter.
Chronicle staff writer Aidin Vaziri contributed to this report.
Annie Vainshtein is a San Francisco Chronicle staff writer. Email: avainshtein@sfchronicle.com