January 28, 2022
8 tips for getting the best results from at-home COVID-19 antigen tests
BY Devon Carter
At-home COVID-19 antigen tests can be very convenient. A positive result can confirm a COVID-19 infection in minutes and help you protect others from infection. And while a negative antigen test result should be confirmed with a PCR test, rapid antigen tests can be a starting point, especially if you have flu-like symptoms.
“A PCR test is always going to be more accurate, but an antigen test can be an option in a pinch,” says laboratory medicine expert Micah Bhatti, M.D., Ph.D.
Looking back a year ago, Bhatti says many of the logistical issues with antigen tests have improved. “Earlier in the pandemic, we had concerns with the antigen test: how to do it, how to interpret what you get and how to capture results, but we’ve come a long way,” he says.
Consider these eight things to ensure you’re getting the most out of your at-home antigen test.
1. Use an FDA-approved test. “The FDA is making sure that the tests that are out there are appropriate for the variants that are circulating,” Bhatti says. Based on the limited data we have to date, antigen tests can detect COVID-19, including the omicron variant. However, it is important to only use antigen test that have undergone rigorous assessment by the FDA and have been granted emergency use authorization. To ensure you’re using an accurate antigen test, check the FDA’s list of antigen tests that have received emergency use authorization.
2. Follow instructions for swabbing. Bhatti emphasizes that each test is different, so to get the best sample, you need to follow the manufacturer’s instructions. “The sensitivity of the assay is highly dependent on getting a quality specimen based on the test’s instructions,” he says.
3. Don’t reuse or share a swab. Antigen tests aren’t always readily available, but using a swab more than once won’t help you get more out of a test kit. It will tamper with results and possibly lead to an infection. “The swabs are sterilized when boxed for your safety and to ensure there aren’t any external factors influencing the results,” Bhatti says. Also, if you’re positive and then share a swab, the other individual is highly likely to get infected if they weren’t already.
It’s also important to only use the swab provided in the test kit. While the swab looks like an ordinary cotton swab, it is made of unique material that has been shown to be compatible with the test. Using a different swab for sample collection will lead to an incorrect result.
4. Avoid moving the test around. Bhatti says antigen tests are designed to be sturdy tests, but he recommends you perform yours in a dedicated space to avoid distractions. “If you accidently bump the test, it will likely be fine, but if drops on the floor, the internal test strip may get damaged,” Bhatti says. He says it's best to not move the test card until after you’ve read the results.
5. Check the results at the recommended time – only. Giving the test more time than stated in the instructions won’t help with sensitivity. In fact, it can actually distort the results. Bhatti recommends you read the results when the time is up and don't come back to it later. “We've seen instances of false positives and false negatives when the tests are allowed to overdevelop,” he says.
6. Dispose of it properly. The materials of an at-home antigen test are safe to be thrown away in your household trash after you’ve read your results, says Bhatti. While the tests materials are safe, make sure not to splash any in your eyes or ingest the contents. “Always read the test kit instructions for proper safety guidance,” Bhatti s.
7. Know how you’re going to share your results, if needed. If you’re required to take a rapid antigen test and share those results, consider how you’ll do so. “At MD Anderson, we accept outside positive test results,” Bhatti says, noting that outside negative test results will not replace MD Anderson COVID-19 testing if your care team determines you need it. Patients should take a photo of their results with their smartphone and upload them to MyChart to share with their care team.
Patients with a positive result from an antigen or PCR test aren’t retested at MD Anderson for 90-days because they are considered protected from reinfection. In addition, PCR tests are so sensitive, a person who has had COVID-19 can test positive sometimes weeks after being infected, even when they’re no longer contagious.
8. Confirm negative results with a PCR test. If you're experiencing symptoms and a rapid antigen test says you're positive, treat it as a positive result. But if you're symptomatic and you have a negative test, you’ll need a molecular PCR test to be 100% sure, says Bhatti.
Some at-home rapid antigen tests recommend testing twice. Bhatti says the intent of doubling up on the test is to capture the ideal window of viral load. Early in an infection, you may not have enough virus. But testing again 48 hours later gives the virus the chance to replicate and produce more proteins that would make the test more sensitive
“It may be helpful to test again if you're symptomatic in a day or two, as there may be more viral antigens,” Bhatti says. Even with two or more negative results from antigen tests, you should consider yourself positive until you can confirm you’re negative with a PCR test.
If you’re testing repeatedly without a good indication, the odds of getting a false result are more likely. Bhatti says it’s like throwing darts.
“Eventually, you’ll hit a bullseye, but that doesn't mean you're an expert. It just means you got lucky and in this case, not in a good way,” he says. He worries that routinely screening for infection in asymptomatic individuals with an antigen test, such as before sending your kid to school or before seeing an immunosuppressed loved one, could result in a false sense of security.
“Even with a negative antigen test, you should wear a mask when in indoors, practice social distancing and wash your hands,” Bhatti says.
Request an appointment at MD Anderson online or by calling 1-877-832-6798.
We've seen instances of false positives and false negatives when the tests are allowed to overdevelop.
Micah Bhatti, M.D., Ph.D.
Physician & Researcher