Testing for active COVID-19 can be confusing. Dr. Leyla Best, Infectious Disease Specialist for UnityPoint Health, explains testing options, advice for where to find them and the science behind how they work.
Which COVID-19 Test Should I Get?
There are two diagnostic tests that identify active COVID-19 infection. A third type, an antibody test, finds evidence of whether you previously had COVID-19.
How Do Antigen Tests for COVID-19 Work?
An antigen test detects proteins produced by the virus. These tests are less sensitive and often less accurate. Antigen tests use a nose swab, a throat swab or a saliva sample to search for active COVID-19 infection. All at-home, self-collected tests are antigen tests. Here’s a quick summary of what to know about the tests.
- Known as: Rapid test or rapid antigen test
- Tests for: Active COVID-19 infection
- Results timeline: 1 hour or less
“The antigen tests work with an artificial antibody that finds the antigen of the virus in the sample. If you are more than a few days into your illness and have a larger virus amount, it’ll be easier for the test to find the antigen on the structure of the virus and detect you as positive,” Dr. Best says.
How Do Molecular COVID-19 Tests Work?
A molecular test includes the rt-PCR test, commonly called PCR test. Molecular tests detect the genetic material that makes up the virus. These tests are very sensitive and often more accurate. Molecular tests look at samples from the nose, saliva, sputum (saliva and mucus) or nasopharyngeal (area up past your nostril) to search for active COVID-19 infection. Molecular tests require a laboratory to determine results.
- Known as: PCR test
- Tests for: Active COVID-19 infection
- Results timeline: Depends on demand, but more than 24 hours
“The PCRs are going to detect any minimal amount of virus, even beyond the point that someone is contagious or ill, but, perhaps, still sheading the virus. That’s why you can get a positive test result from a molecular test, even though you might not have an active COVID-19 infection.” Dr. Best says
How Do Antibody COVID-19 Tests Work?
An antibody test doesn’t test for active COVID-19 infection. Instead, these tests use a blood sample to determine if you've developed antibodies against the COVID-19 virus. If antibodies are identified, it’s a sign you might have previously contracted COVID-19.
- Known as: Serology test
- Tests for: Prior COVID-19 infection
- Results timeline: Several days, even up to a week
If you’ve had a COVID-19 vaccine, an antibody test may also pick up on the antibodies you developed from the vaccine.
What Kind of COVID-19 Test Do I Need?
There are a variety of options for COVID-19 tests, including healthcare facilities, community testing sites and at-home test kits. Depending on your symptoms (or lack thereof), check out our guide to determine what’s best for you.
Where Can I Get a COVID-19 Test?
Depending on the spread of COVID-19, tests may be hard to find. Try checking your local pharmacy or retailer. If there are no tests at the store location near you, check their website to see if you can get one shipped to your home. If you’re able, look often for when they restock. State and local health departments usually have an option you can try, too. Below you’ll see the links for the states we serve.
Finally, you can order free at-home tests online from the federal government.
Why Are There So Many Coronavirus Test Types?
“There have always been different testing options for respiratory viruses. We’re now just more aware of them, since there is more testing occurring in our communities during this pandemic,” Dr. Best says.
Can Current COVID-19 Tests Identify All the Emerging and Future Variants?
Some are questioning the current tests with the emerging COVID-19 variants. The good news is the FDA approved antigen and molecular tests can still identify COVID infection.
“With the variants, some have questioned the ability of the at-home antigen tests. It’s not uncommon to get a false-negative result from those tests. They’re able to detect all current virus variants, but rapid tests require more virus to become positive. In other words, a negative test on day two or three of the illness doesn’t mean you’re necessarily negative of COVID-19. If you have any respiratory symptom, it’s a good idea to repeat the at-home test a couple of day later, when there’s more virus replication to double check your status,” Dr. Best says.
How Long Does It Take to Get COVID-19 Test Results?
Usually, antigen tests give you results in less than an hour. Molecular tests take longer. For PCR, which is a common type of molecular test, results typically return in 24-48 hours. However, in times of high demand, results may be delayed up to seven days. Timing depends on how many tests the lab is handling and how quickly technicians can get to your sample.
If you get a test at UnityPoint Health, the quickest way to get your results is to get a MyUnityPoint account to view your results as soon as they’re available.
What Happens to My COVID-19 Test Sample?
Antigen tests used at healthcare facilities or in your home, work similarly to a pregnancy test, which is why you get a rapid result.
“For PCR tests, the sample is taken to a central lab and prepared by technicians who put samples in a machine called a thermocycler. These machines multiply the genetic material several times, sort of like making copies on a copy machine, to determine if any virus is present,” Dr. Best says.
Should I Get Tested Before or After Travel?
The CDC recommends delaying traveling unless you’re fully vaccinated. Traveling without being vaccinated will increase your risk of getting, and spreading, COVID-19.
If you plan to travel domestically, follow these CDC recommendations:
- Check testing requirements. Before you go, check in with your airline and destination to review testing requirements as well as any other pandemic-related documentation or restrictions.
- Get tested before you go. Unvaccinated, domestic travelers should get tested one to three days before travel. Keep results on hand, if needed.
- Get tested when you return. Unvaccinated, domestic travelers should get tested three to five days after returning and self-quarantine for five days.
International travel poses additional risks, and even fully vaccinated travelers have an increased chance of getting, and possibly spreading, new COVID-19 variants.
If you plan to travel internationally, follow these CDC recommendations:
- Check testing requirements. Before you go, check in with your airlines and destination to review testing requirements, find testing locations and any other pandemic-related documentation or restrictions.
- Get tested before you return. All travelers, regardless of vaccination status, must be tested before returning to the U.S. You must get tested no more than one day before your flight departs.
- Carry testing documentation. If traveling back to the U.S., be prepared to show documentation of a negative COVID-19 test. Check with your airline to determine requirements, including what information your document must include and if it’s allowed to be digital or printed.
The CDC says masks are required on planes, buses, trains and other forms of public transportation while traveling into, within or out of the United States.
Why Isn’t Testing Without Any Symptoms (Asymptomatic Testing) Reliable?
If you’ve been exposed to COVID-19, you can begin showing symptoms any time within the virus’ 14-day incubation period. If, for example, you don’t have symptoms on day four following exposure and get a COVID-19 test, your results only apply to that day. You could still go on to develop the infection.
If you have been exposed to the virus, the best advice is to follow the CDC’s guidelines on testing and quarantine.
What Does My COVID-19 Test Result Mean?
Test results for antigen or molecular tests can come back in two ways:
- Positive. You have been infected.
- Negative. You are not currently infected.
However, Dr. Best says your test could be a false negative or a false positive.
- False negative. You are infected, but the test says you are not infected.
- False positive. You are not infected, but the test says you are infected.
“When transmission of the virus is high, you have symptoms and you get a positive antigen test, it means you have the virus. The performance of each test platform depends on the community activity of that specific virus. If the activity of the virus is low, you have no symptoms and you get a positive antigen, that may represent a false positive,” Dr. Best says.
If you don't think your test results are correct, talk to your doctor or consider another testing option.