05:08 AM

Everything you need to know about COVID-19 testing from a chief pharmacy officer

LOS ANGELES — Recently, many Americans found themselves with a new unwanted pastime: searching for COVID-19 tests. The government is now offering four free at-home tests to every household, and health insurance companies are reimbursing for additional tests.

How will these developments affect testing, what are the differences between the COVID-19 tests available and when is the best time to test? Krist Azizian, PharmD, MHA, chief pharmacy officer for Keck Medicine of USC, addresses any confusion. 


Every home in the U.S. is now eligible to order four free at-⁠home COVID-⁠19 tests. What types of tests are offered?

These tests are antigen tests. Antigen tests detect a high volume of viral load, and the results are generally available within 15 minutes. You can order the free at-home tests here.

How will these free tests change testing?

Allocating four at-home tests per household will make testing more accessible. If your household requires more than four tests, you may be eligible to be fully reimbursed for tests you purchase or get them free of charge through an insurance reimbursement program that launched Jan. 15. You can contact your health insurance provider for further information.

Additionally, the government also has created an online resource to help Americans find local low or no-cost testing. While manufacturers are working hard to keep up with the demand for at-home tests, it will probably take a few more months for them to get totally up to speed.  

How do you know which at-home test to get? There are so many on the market.

The U.S. Food and Drug Administration has authorized the emergency use of several different brands of at-home tests, and you should choose from one of these. You can find the list here.

If a family needs more home tests but can’t find them, is it okay for more than one person to share a test – both use the same swab?

Absolutely not. These tests are for single application only. People are taking a tremendous risk of exposing others by using one swab for multiple family members. If one has COVID-19 and the others don’t, sharing a swab almost guarantees everyone will get it.

Labs and clinics also offer antigen testing. Are lab or clinic tests better or more accurate than over-the-counter, at-home tests?

Not necessarily. Antigen tests conducted at a clinic or lab are very likely comparable to tests purchased over the counter. The only reason lab testing may be more accurate is because some people may use the at-home tests incorrectly or may misinterpret the results.  

How is a PCR test different from an antigen test?

PCR tests are generally analyzed in a lab and are considered the gold standard for diagnosing COVID-19. Testing results usually take a few days unless you get a rapid PCR test, which allows you to learn the results in a few hours. The tests are much more sensitive than antigen tests, meaning they can detect a lower viral load than an antigen test. They are also less likely to produce inaccurate results, both negative and positive.

Is it possible to find free PCR tests?

Some workplaces and schools offer free PCR tests, and some health insurance providers reimburse PCR tests ordered by your health care provider. You may also find local sites or pharmacies that offer free PCR testing. For example, Los Angeles County offers free at-home PCR tests that people can pick up and return for lab analysis.  

What is the timeline for getting tested if someone is exposed to COVID-19?

COVID-19 has an incubation period of five to seven days, so you should get tested at least five days after exposure or upon the onset of symptoms.

Which type of test is best after exposure?

If you are asymptomatic, a PCR test is your best option because it detects COVID-19 at a much lower viral load. In general, viral load correlates to symptoms. If you are asymptomatic, your viral load may be too low to be detected by an antigen test. (Please note, however, that even if you are asymptomatic, you may still be contagious.)

If you have symptoms, you can take either an antigen test or a PCR test because symptoms generally mean your viral load is higher, which both tests should detect. If you test negative on an antigen test, for greater reassurance, follow up with another antigen test at least 24 hours later or a PCR test.

While antigen tests are fairly accurate in detecting positive results, if you test positive on an antigen test, it’s best to follow up with a PCR test. However, you should quarantine upon receiving a positive result from any test.

Some workplaces are recommending a negative antigen test within five to 10 days of testing positive or after symptom onset (as long as symptoms are resolving) to allow employees to return to work. The rationale for this is that a negative antigen test, along with symptom resolution, indicates a low viral load with minimal chance for transmission. 

What is the biggest testing mistake you see?

The biggest testing mistake I see is people taking tests too soon before the viral load can be detected. Testing too soon can waste at-home tests, cause people to needlessly spend money on lab tests and give them a false sense of assurance should they test negative. Testing is a very effective tool for detecting COVID-19; however, it’s best to wait at least five days after exposure to test.