Everything you need to know about COVID-19 diagnostic tests

So you’ve got COVID-19 symptoms or maybe you just found out you’ve been exposed to someone who has the virus. It’s time for a test, but what kind should you get? Will it detect omicron? What should you do if you test positive?

Below Michael Myint, MD, an infectious disease specialist and epidemiologist with MultiCare, and Mary Fairchok, MD, a pediatric infectious disease specialist at Mary Bridge Children’s answer common questions about COVID-19 testing.

What types of diagnostic tests are available for COVID-19?

There are two main types of tests that determine a current COVID-19 infection: antigen tests and molecular tests.

Molecular tests: These tests search for traces of the virus’s genetic material. The most common type of molecular test is the polymerase chain reaction (PCR) test. Whether taken at home or at a designated testing site, the results must be processed by a lab.

“The PCR test is the most accurate test that’s available because it can detect very low levels of the virus,” says Dr. Fairchok.

Antigen tests (also known as rapid tests): Antigen tests identify proteins from the virus. These tests are fast (often providing results in approximately 15 minutes) and can be fully completed at home.

“While convenient and relatively inexpensive, the downside to these tests is that they aren’t as sensitive as PCR tests, so they are less likely to pick up early cases of COVID-19 or infections where there are no symptoms,” says Dr. Myint.

How reliable are these tests in detecting omicron?

Overall, antigen tests and molecular tests perform well at detecting omicron and other known variants. However, both tests may be less likely to identify an early-stage infection with omicron than previous variants.

“If you’re experiencing COVID-19 symptoms and you get a negative test result from an at-home rapid test, take it again in 24 hours.” says Dr. Myint. “If you get a positive result, you can be confident that it’s accurate.”

I’m having trouble finding a test. Can I just go to the emergency department or an urgent care center to get one?

Unless you are experiencing severe symptoms, such as shortness of breath, you should not go to an emergency department. We also recommend that you do not walk into an urgent care center to get a COVID-19 test, as both EDs and urgent cares are experiencing very high patient volumes.

Instead, seek out a community testing site or schedule a virtual visit with MultiCare Indigo Online Care, which can direct you to an appropriate Indigo location for testing as needed. An at-home testing kit may also be an option depending on your situation.

Should I keep a stock of tests at home and what kind should I get?

Yes, it’s helpful to keep a few boxes of tests at home. As the omicron variant continues to spread rapidly, timely appointments at testing sites have become more difficult to obtain. There are several situations where having a cache of these tests on hand can be useful:

• You’re experiencing COVID-19 symptoms and wondering if you’re infected.
• You’ve been exposed to someone with COVID-19.
• You intend to visit a friend or family member who has a high risk of developing severe symptoms should they contract COVID-19.
• You’ve been diagnosed with COVID-19 and are wondering if it’s safe for you to leave isolation. If you test negative on an at-home rapid test, it’s likely that you’re no longer contagious. However, it’s still important to follow guidelines from the Centers for Disease Control and Prevention (CDC), which include wearing a well-fitted mask in public.

As far as what tests to get, only purchase tests that have been approved by the U.S. Food and Drug Administration (FDA). The FDA maintains a list of approved COVID-19 antigen tests as well as molecular tests. Antigen (rapid tests) are generally faster and cheaper, though slightly less accurate than molecular tests. At-home test kits of both varieties can be purchased online and at most pharmacies, though given current demand, they may be challenging to find.

“There are some counterfeit tests out there as well as a few that have been pulled from the market, so make sure you purchase tests from a legitimate vendor,” says Dr. Fairchok.

The Biden Administration has recently announced two initiatives intended to make COVID-19 testing more widely available. The newly launched website, COVIDtests.gov, allows every household in the Unites States to order free at-home rapid tests for mail delivery. Also, starting Jan. 15, all private health insurers are required to cover at-home COVID-19 tests at no cost.

What if I have an at-home testing kit that has expired?

Under normal circumstances where you can easily obtain COVID-19 testing, you should discard at-home tests that have passed their expiration date. However, if that’s all you have access to — given the current pressures facing testing facilities, urgent care centers and hospitals — it’s okay to take it but be wary of the results.

“If you take an expired at-home test, you should trust the results less — both a negative and a positive,” says Dr. Myint. “It depends on how far past the expiration date the test is. If it’s a day or two past, the results may still be valid. If it’s weeks past, then the validity is much less certain. It would be prudent to make an appointment for a PCR test in either scenario.”

What if I don’t use an at-home test as directed?

While the science behind COVID-19 testing continues to evolve, the diagnostic tests currently available have been designed and approved for use in a specific way.

“Deviating from the instructions — swabbing the throat instead of the nose for example — can lead to inaccurate results,” says Dr. Myint. “You could cause a false positive or false negative. It’s best to follow the instructions and use the tests as intended.”

I’ve tested positive for COVID-19 on an at-home testing kit. What should I do now?

You can be confident that a positive result from an at-home antigen test, when used correctly, is accurate, so you shouldn’t need to get a follow-up PCR test to confirm your results. What you do next depends on the type of symptoms you are experiencing and whether you are at high risk for severe disease.

• Not high risk, mild symptoms. If you are not a person who is at high risk of severe disease and you are experiencing no symptoms (asymptomatic) or mild symptoms, the best course of action is to stay home, isolate yourself from family members as much as possible, stay hydrated, get rest and take Tylenol or ibuprofen as needed. There’s no need to call your provider at this time.
• Not high risk, concerning symptoms. If you develop an uncontrollable cough or fever, experience increasing shortness of breath or cannot eat or drink, then you should contact your provider immediately. If your symptoms are urgent — for example, you are dizzy or can’t breathe — call 911.
• High risk, regardless of symptoms. If you are a person who is immune compromised, has a chronic condition or other factors, such as age, that put you at high risk for severe disease, you should contact your provider, even if you are not having symptoms yet or the symptoms are mild.

“Though they are in limited supply, there are now FDA-approved medications for some high-risk individuals who test positive for COVID-19,” says Dr. Fairchok. “These medications can help prevent the progression to severe disease.”

I’ve been exposed but I tested negative on an at-home rapid testing kit. What should I do now?

Next steps depend on your particular situation.

You have symptoms. If you’re symptomatic and you’ve tested negative on an at-home rapid testing kit, there’s still a high probability that it’s COVID.

“In this situation, I recommend treating it as if it may be COVID — in the sense of isolating yourself from other members of your household and making an appointment for a PCR test,” says Dr. Myint.

You don’t have symptoms. If you aren’t experiencing symptoms and it’s been less than five days since your exposure, it’s possible that an at-home rapid test has not detected your infection yet. It’s a good idea to repeat the test in 24 hours. It’s also important to keep in mind that you may still be contagious.

“You still have to be very careful and wear your mask, and I recommend scheduling a PCR test, since it’s more accurate,” says Dr. Fairchok.