MONDAY, Jan. 10, 2022 (HealthDay Now) -- The surge of the Omicron variant across the United States has left people scrambling to find at-home COVID-19 test kits.
"Tests are in short supply, there's no doubt about it, because of the sheer volume of people wanting and needing to get tests," said Lori Tremmel Freeman, chief executive officer of the National Association of County and City Health Officials. "The demand is high and we want people to test. The problem is we want them to be able to get it."
The appeal of at-home tests is clear -- you are in charge of the process. You collect the sample, usually by swabbing the inside of your nose, and in the case of rapid tests you perform the lab work at your own table or counter. Usually you'll get results within minutes.
Here's what you need to know about how these home tests work, where you can look for them, and when it is best to use them.
Which tests can you take at home?
There are two main types of COVID-19 tests you can administer at home -- antigen tests and PCR tests.
Antigen tests are the ones considered "rapid" tests, because they return results in under an hour. They look for proteins on the surface of the coronavirus that provoke an immune response from your body.
There are more than a dozen U.S. Food and Drug Administration-approved antigen tests. Popular brands include Abbott's BinaxNOW, Quidel's QuickVue, OraSure's IntelliSwab, BD Veritor's At-Home and the Intrivo On/Go.
PCR tests look for the actual genetic material of the virus. They're more accurate than antigen tests -- in some cases, too accurate -- but while you take a sample yourself at home, you usually have to either drop it off at your doctor's office or mail it to a lab to get results. It can take one to three days to hear back.
Common brands of PCR tests include LabCorp's Pixel, DxTerity and Everlywell.
How accurate are they?
Rapid antigen tests are fairly accurate, especially if you have COVID symptoms, because at that point you have high levels of detectable virus in your body. A positive test not only means that you've got COVID, but that you're more likely to be contagious.
"They are great at answering the question, 'Is it safe to be around me?'" said Dr. Amesh Adalja, a senior scholar with the Johns Hopkins Center for Health Security in Baltimore.
Antigen tests are more likely to return a false negative if you're infected but haven't yet developed symptoms. But at that stage, "if you have such a small amount of virus, you're not likely to be very contagious to others," noted Dr. William Schaffner, medical director of the National Foundation for Infectious Diseases.
Looking for certainty? PCR tests are considered the "gold standard" for detecting and diagnosing COVID, but they have their drawbacks as well.
PCR tests are so accurate that they can detect the genetic material of old coronavirus debris in your body, long after you're well and all the live virus inside you has been eliminated.
"The PCR test can continue to be positive for a substantial period of time, literally weeks," Schaffner said. "It's not really a good test for getting you out of isolation."
There have been concerns that some antigen and molecular tests might not be able to detect the Omicron variant as well as prior COVID variants. The FDA has noted this concern, but is still investigating.
Where can you find a test?
Antigen tests are sold over the counter and are available at pharmacies, big-box stores like Walmart and Target, and online retailers like Amazon.
However, as many consumers have found out, the Omicron surge is causing spot shortages of the tests. "It's not always available at every pharmacy that you go in and want to buy it," Schaffner said.
Before running out to the pharmacy, you might want to first call your doctor's office or community health center to see if they have any rapid tests on hand, Freeman suggested.
"If you are a patient at a community health center or a rural health center, your best bet is going to be to contact your provider and those tests should be available at those centers," Freeman said.
You also should check with your local health department, to see if test kits are being handed out anywhere in your community. For example, "there are libraries, at least in my area, that have been distributing free tests as well," Freeman noted.
President Joe Biden has promised to make 500 million test kits available to Americans, on top of those already available for purchase. The Washington Post reported Friday that the White House is finalizing plans to start shipping the kits by mid-January, including a website that would allow people to request a rapid test.
As with N95 respirators and other COVID-linked supplies, buyers should also be wary of fake products. The FDA maintains a list of approved antigen tests; try reviewing that list before buying.
How much will you pay? A two-pack of rapid antigen tests has cost as little as $14, but retailers like Kroger and Walmart have started raising prices following the lapse of a 2021 deal with the White House to sell the tests at a reduced rate. Tests like BinaxNow are available for around $24 at pharmacies and stores, and about $20 at Walmart.
Price-gouging is also on the rise, however: CBS News reported Monday that some online sites are now charging double or triple for tough-to-find test kits.
Biden has said that insurance companies will pay for at-home testing beginning in January, but the details of how that would work have not been announced yet.
When should you test?
You shouldn't use an at-home rapid antigen to test yourself immediately after you've been exposed to COVID, experts say. Even if you have been infected, the virus probably hasn't had a chance to replicate itself to detectable levels.
"The tests are most accurate when you've developed symptoms, because that's when you have the most virus in your throat," Schaffner said. "Many people after what they think is an exposure run out the next day or the day after and do the test. Well, the test is not likely to be positive at that point. It's too early."
Instead, the U.S. Centers for Disease Control and Prevention recommend that people without symptoms who have been exposed to COVID get a PCR test, which can detect even minute amounts of virus in your body.
Antigen tests should mainly be used to make sure that you're safe to be around before traveling or attending a gathering or event, even if you don't have symptoms, experts said.
"Antigen tests are excellent tools for determining if someone has enough viral shedding to infect someone else, so are very useful as screening tools for asymptomatic individuals wanting to know their status before social interaction," Adalja said.
Schaffner said he and his extended family relied heavily on home testing during the holidays. They're all vaccinated and boosted and all wear masks, but the tests provided added relief for their family gatherings.
"We decided the morning of Thanksgiving and the morning of Christmas for all of us to do a rapid test. We were all negative," Schaffner said. "That reassured us so that when we did get together, we decided to take off our masks. That gave us an additional level of assurance and some comfort that we could do that safely."
Antigen tests can be used to help figure out if your symptoms are COVID, but you should follow up the home test with a more accurate PCR test, experts said.
Keep in mind that you still might get a negative test even if you've got COVID with symptoms. "If one is sick, a negative test should prompt repeat testing, more formal testing and evaluation for other causes of symptoms," Adalja said.
The CDC does not recommend that people take a test before emerging from quarantine, and for good reason, Schaffner says. Either the antigen or the PCR test can give a false result that would either keep you in quarantine when you're well or lead you to not take proper precautions when you're still infectious.
"Most people would like an explicit yay or nay answer. Life is more complicated than that," Schaffner said. "That's why the CDC didn't tack on testing as a way for you to get out of either isolation or quarantine -- because they knew about the limitations of the tests."
The U.S. Centers for Disease Control and Prevention has a COVID-19 Viral Testing Tool that will help you figure out when and how to get tested.
SOURCES: Lori Tremmel Freeman, chief executive officer, National Association of County and City Health Officials; Amesh Adalja, MD, senior scholar, Johns Hopkins Center for Health Security, Baltimore; William Schaffner, MD, medical director, National Foundation for Infectious Diseases