How accurate are COVID-19 rapid tests? Should you test before holiday gatherings?

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The surge of the delta COVID-19 variant is driving sales of at-home COVID-19 test kits, which offer quick and fairly accurate results — if you use them correctly. Here, we answer some common questions about the quality of at-home tests, how to use them and what to do with the results ahead of the holidays.

This year, holiday planning is being upended by COVID-19 variants, including omicron, which are on the rise. The good news is that there’s at-home COVID-19 testing available this year. There are multiple vaccines available, and boosters are now recommended for everyone 18 and older who already received a primary vaccine series.

For the holidays, some people will be gathering with larger groups from separate households or with people who are high- risk for severe COVID-19, such as the elderly or immunocompromised. The best thing you can do is get vaccinated and boosted for COVID-19.

But regardless of your vaccination status, you can also self-test before gatherings using at-home COVID-19 tests.

How do rapid tests compare to lab or doctor’s office tests?

Although there are many different COVID-19 tests available, they can generally be broken down into two types: molecular and antigen tests.

Molecular tests include nucleic acid amplification tests (NAAT) such as polymerase chain reaction tests (RT-PCR or PCR tests). They’re usually processed in a laboratory and are generally more accurate than antigen tests, but results can take longer.

At-home rapid tests are antigen tests, which use a different mechanism to detect infection. These tests can be processed right in your home using a kit that looks similar to an at-home pregnancy test and gives results within 10-15 minutes.

Antigen tests are still fairly accurate, particularly when someone is experiencing symptoms and their viral load is very high. However, they can be less accurate when someone has a lower viral load, such as in someone without symptoms. This could lead to false negative test results. You could have a false negative result if, for example, you test yourself too soon after you’ve been exposed to someone with COVID-19, or if you test when you have no symptoms.

Is one at-home COVID-19 test better than another?

Each test maker is required to submit clinical data about the sensitivity (the ability of a test to detect a true positive) and the specificity (the ability of the test to detect a true negative) of the test. Because all at-home COVID-19 tests are allowed under an emergency use authorization from the U.S. Food and Drug Administration, the relative performance of individual tests hasn’t been as rigorously tested by the FDA — so it’s really difficult to say if one is “better” than another.

Are there any advantages to testing at home?

The major advantage is comfort and convenience — and the ability to get test results within 10-15 minutes.

Should you test at home for COVID-19 if you have no symptoms? What if you had close contact with a COVID-19-positive person or you plan to gather with people outside your household for the holidays?

You may consider doing COVID-19 testing ahead of time as another level of precaution before holiday gatherings. If possible, taking an at-home rapid COVID-19 test the day of the event is ideal.

While these tests aren’t 100% accurate, a negative result strongly suggests that you’re not contagious at that particular time.

It’s important to understand the limitations of the test — there’s a possibility for a false negative test, especially if you test too early after a possible exposure. The Centers for Disease Control and Prevention (CDC) recommends testing 5-7 days after your last exposure, if you’re fully vaccinated.

If you’re not fully vaccinated, the CDC recommends testing immediately after finding out you’ve had close contact with someone who has COVID-19. If results are negative, test again 5-7 days after last exposure — or immediately, if symptoms develop.

Serial testing — meaning repeating the test several days earlier before the actual gathering — can help improve accuracy of your results.

Some may choose to quarantine before an event, just as some did last year prior to the COVID-19 vaccine rollout. Quarantining prior to an event probably isn’t necessary for everyone (especially for fully vaccinated individuals). The decision for family/friends to quarantine ahead of time is a personal decision based on individual risk tolerance.

What steps should you follow to ensure you’re doing an at-home COVID-19 test properly?

It’s very important to follow the instructions from the manufacturer carefully. Read through the instructions and be sure you understand prior to opening the test kit. Wash your hands and surfaces before starting the test.

If you don’t swab the nostrils properly, you may end up with a false negative test, so again, follow the instructions in the kit. You may feel uncomfortable swabbing this deeply into your nose or the nose of a loved one, but swabbing is fairly quick, and doing it correctly will improve the likelihood of an accurate test.

What should you do if your at-home COVID-19 test is positive?

If your at-home test is positive, you should notify your health care provider and follow CDC guidelines for quarantine and isolation. It's also important to notify anyone you’ve been in close contact with so they can take the proper steps of testing and quarantine to help limit the spread of infection to others.

Does a negative home test mean you’re in the clear?

If you followed the instructions of the test carefully and you get a negative result, it’s unlikely that you have COVID-19 at that time. However, there are some circumstances where you may get a false negative result, particularly if you test too early in the course of the infection (when viral load is not as high). If you’re concerned about this, you could repeat the test a few days later.

How much do at-home tests cost? What if you can’t afford the cost?

COVID-19 rapid tests cost roughly $20 to $40. If you can't afford the cost of an at-home test, free COVID-19 testing is available at multiple locations. Some public libraries and local public health organizations have free COVID-19 rapid tests available for the public.

Other useful tips to keep in mind before gathering together this year:

Get your flu shot. COVID-19 isn’t the only contagious respiratory virus. There’s also the flu. The CDC has reported an uptick in flu cases as the flu season begins, even though overall national cases are down. Yes, it’ is possible to contract both COVID-19 and the flu at once, which would be a double whammy.

Unvaccinated guests should wear masks. Those who haven't been fully vaccinated should wear well-fitting masks, and if weather permits, consider celebrating outdoors. Outside events are generally safer than indoor ones.

If you’re sick, stay home. It’s not worth taking a chance to infect your loved ones if you’re unwell.

What to keep in mind with the omicron variant

There’s still a lot we don't know about the omicron variant, including:

• Whether it’s more transmissible

• If there’s increased disease severity

• How effective the vaccine will be against it

We’ll likely have a lot more data about this in the coming weeks, so my advice is to be prepared to be flexible with holiday plans. Get your COVID-19 vaccine as soon as possible, because the delta variant is still widespread in the U.S. and we know the vaccine is highly protective against it.

Ashley Lipps is an infectious diseases physician at The Ohio State University Wexner Medical Center and an assistant professor in the Division of Infectious Diseases at The Ohio State University College of Medicine.