|Usually antigen tests
|PCR or antigen tests
|Detect current infection
|Detect current infection
|Results in 10-30 min
|PCR results might take up to three days. POC results might take less than one hour.
|Antigen tests are less accurate than PCR tests.
|PCR tests are more reliable if you test negative.
You might do point-of-care (POC) testing in a healthcare provider’s office, urgent care center, or emergency room. POC testing is testing at the health site in order to get results sooner. These tests might be antigen or molecular (e.g., PCR) tests. As with other antigen and molecular tests, there is a bit of a trade-off:
- Antigen test results are faster, which means these tests can detect COVID sooner and possibly prevent the spread of the virus. However, they aren’t as sensitive at detecting the virus and might give false negatives, especially if you’re asymptomatic (do not have symptoms).
- Molecular test results take longer, but these tests are more accurate at detecting the virus whether or not you have symptoms.
If you receive negative results with an office or emergency room POC antigen test, do another at-home test 48 hours later, just as you would with a negative at-home antigen test.
Though antigen tests aren’t as accurate as PCR tests, they can still be very helpful in detecting COVID-19. Here are some tips for ensuring accurate results with at-home testing:
- Make sure the test isn’t expired, as this can make the test less reliable. (If the test is past its shelf-life, look on the FDA website to determine if its shelf-life has been extended.)
- Follow the test’s step-by-step instructions, as user mistakes can influence results. This includes swabbing correctly and checking results at the specified time.
- Have several tests at home so you can test 48 hours after a negative result. You can use different brands.
- If you test negative again after 48 hours even though you think you were exposed to COVID, perform a third test 48 hours later. If you still test negative, consider a PCR test or consult with your healthcare provider.
Always dispose of used tests safely and never share or reuse a test.
Viral tests diagnose active COVID-19 infections. Polymerase chain reaction (PCR) and antigen tests are the most common viral tests.
PCR COVID tests are the “gold standard.” PCR tests are molecular tests. They work by detecting the genetic material of SARS-CoV-2, the virus that causes COVID. A healthcare provider will collect a sample, typically mucus or saliva, and send it to a lab for testing. Results can take up to about three days.
PCR tests are highly sensitive, making them more reliable than antigen tests. PCR tests can detect SARS-Cov-2 from the earliest stages of COVID infection up to three months after you recover.
You are likely not contagious if you test positive with a PCR test after you recover. Research has found that the virus can likely not replicate and spread about nine days after symptom onset.
Antigen tests tell whether you have an active COVID infection. Antigen tests are useful for POC testing. In contrast to PCR tests, antigen tests have a quick turnaround time, usually within 30 minutes.
Most at-home tests are antigen tests. At-home tests allow you to collect your own sample and get results within minutes. At-home tests might be easier to use and less intimidating than testing in healthcare settings.
Antigen tests are less sensitive and more likely to deliver false-negative results than PCR tests, especially if you don’t have symptoms. You likely have COVID if you test positive with an antigen test. The CDC advises taking a second antigen test 48 hours after your first to confirm a negative result if you have symptoms. You might need a third antigen test 48 hours after your second if you are asymptomatic.
You can provide different sample types for a COVID test, typically a blood or mucus sample. Your sample type might depend on the test.
A healthcare provider will insert a needle into your arm to draw blood for an antibody. You might feel a sting when the healthcare provider inserts and removes the needle. Bruising or pain might occur after a blood sample, but those side effects usually go away quickly.
Antigen tests usually require a nasal swab. You will also provide a nasal swab for a PCR test. A healthcare provider will typically take a nasal swab from the front or back of your nostrils or the uppermost part of your nose and throat. A nasal swab can be uncomfortable, causing you to cough or gag. A healthcare provider might ask you to take a nasal swab yourself. You will perform the nasal swab if you take an at-home test.
Getting a COVID test at the right time ensures your results are as accurate as possible. The CDC advises testing right away if you have COVID symptoms. Remember that a singular negative antigen test cannot rule out an active infection. You might require repeat antigen testing or a PCR test to confirm a negative result.
In contrast, you might wait five days after a possible exposure if you do not have symptoms. Testing if you do not have symptoms but might have had an exposure helps reduce the spread of COVID.
Consider testing if you plan to attend an event or take a trip where you might expose people, especially those likely to get very sick from COVID. You might also want to test within one to two days of an event or trip.
No test can determine whether or not you’re contagious. The CDC advises relying on symptoms rather than test results to figure out when you can safely end your isolation.
Antibody tests, or serology tests, look for antibodies to SARS-CoV-2. Antibodies are proteins your immune system produces to fight off a foreign invader, such as a virus.
An antibody test cannot diagnose active COVID-19 infection. Instead, your results can determine if you have had the virus. Antibody tests provide information on how many people have had COVID and the frequency of asymptomatic cases.
Research has found that antibody tests have an accuracy rate of nearly 99.23%. Your body might not produce antibodies until one to three weeks after infection. Therefore, an antibody test may not be accurate if you test too early.
The presence of antibodies suggests that you’ve previously had COVID or have been vaccinated. However, it cannot determine immunity from COVID after vaccination.
The Food and Drug Administration has not authorized any at-home antibody tests. The Food and Drug Administration approved an antibody point-of-care test in September 2020 for healthcare providers to use. Antibody point-of-care tests can provide results within 15 minutes using a blood sample.
Follow the CDC’s instructions for testing if you have had COVID within the past 90 days:
- If it’s been 30 days or less, and you have symptoms: Take an antigen test. Repeat negative tests if needed.
- If it’s been 30 days or less, and you do not have symptoms: The CDC does not advise testing.
- If it’s been 31–90 days or less, and you have symptoms: Take an antigen test. Repeat negative tests if needed.
- If it’s been 31–90 days or less, and you do not have symptoms: Take an antigen test. Repeat negative tests if needed.
You have a few options for a viral COVID-19 test, such as an antigen or PCR test. You’ll need to receive an antibody test at a healthcare facility.
Check the following places for a viral COVID test:
- A healthcare provider: Consult a healthcare provider if you are unsure what kind of COVID test is right for you. They might be able to give you a test in their office.
- Online or at a store: You can purchase at-home tests at your local pharmacy or grocery store, or order them online. Ensure that the Food and Drug Administration has approved any at-home test you are buying.
- Your local or state health department’s website: You can find information on where to find a testing center that provides antigen or PCR testing.
There are a few ways to diagnose active or past COVID-19 infections. Viral tests, including antigen and PCR tests, determine whether you currently have COVID. Antibody tests look for antibodies against SARS-CoV-2 that your body develops after a previous COVID infection or vaccination.
You can find at-home tests at the store or online. Consult a healthcare provider or search for in-person viral or antibody testing on your local or state health department’s website. Talk to a healthcare provider if you are unsure which type of COVID test is right for you or when to take one.
The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it’s possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.