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How Accurate Is Pcr Covid Test - .Which COVID Test Should You Get? > News > Yale Medicine
Ronald Lubelchek, MD, is a board-certified physician and medical director in Chicago, Illinois who specializes in infectious diseases. Testing rates decreased for a time once vaccines became available and the numbers of new cases started to decline. However, new variants and a desire to return to a semblance of normal life have increased the demand for tests again.
There are more options for testing now than there were at the start of the pandemic. Lab testing is still available, but new types of at-home tests have made testing easier. Polymer chain reaction PCR tests are typically performed in a laboratory or healthcare setting. Using a swab, you or a technician will collect a sample of cells from your nose, mouth, or throat. After collection, the samples are treated with an enzyme solution and examined under extreme amplification copied multiple times.
The technique allows test centers to identify the exact genetic materials in the sample, including the identity of a specific virus. The test can also differentiate between different variants—or strains—of a virus.
The downfall to the process is the time that it takes and the fact that lab analysis is required to get results. PCR tests can be performed quickly when there is an urgent need, but they take at least a few hours to produce results. If you are not close to the lab that is doing your test, it can add extra time. Increased demand and the number of tests a particular lab is responsible for can also delay your results.
The hours that the test takes to complete can turn into days when distance and demand are factored in. In mid, the Food and Drug Administration FDA began approving at-home PCR test kits that allow you to collect a sample at home and then send it to a lab for testing. There are also a few options for nucleic acid amplification tests that can be used at outpatient clinics and can provide a result in about 20 minutes.
These tests look for nucleic acid from the virus instead of antigen. These tests are quick and are often used to detect other viruses that cause illnesses like the flu, respiratory syncytial virus RSV , and sexually transmitted infections STIs. They can also produce results in under an hour. Antigen tests are not as sensitive as PCR-based or other nucleic acid amplification tests.
There is a time and place for each type, and which one you choose will depend on your situation and symptoms. For example, if you are sick and wondering whether your symptoms could be caused by COVID, a rapid test can give you that answer quickly. That's helpful because it would allow you to isolate yourself from other people to help reduce the spread of the virus. However, if you do not have symptoms or you're simply taking a test before an event to make sure that you're not sick, a rapid antigen test may not be able to give you the most accurate result.
People who are symptomatic who need testing before a medical procedure, people who are testing because they were exposed to someone with COVID, or people who remain sick despite numerous negative rapid tests are the best candidates for PCR testing. While this type of testing takes longer and is more expensive than rapid tests, it can provide you with the most accurate result. Rapid antigen tests can be more effective if you need to do repeated serial testing.
The COVID test that you choose will depend on how you are feeling, why you are taking a test, and how vulnerable the people around you are to getting sick. If you need immediate results, a rapid antigen test might be the best option.
However, if you need the most accurate test, or you are still sick and want to validate your rapid test result, PCR is the better choice. If you have questions about COVID testing, symptoms, or treatment, talk to your doctor or another trusted healthcare provider.
You can collect samples for both PCR and rapid antigen tests at home, but you can only get immediate results with a rapid antigen test. A PCR test must be sent to a lab where special equipment is used to analyze your sample. PCR tests are generally considered more accurate than rapid tests, but rapid tests have benefits that PCR tests do not have—for example, they provide results faster and for a lower cost.
The test that is right for you will depend on why you are taking the test and how soon you need to get results. Both PCR and antigen testing use samples of cells collected from your nose, mouth, or throat. After collection, PCR testing requires special equipment in a lab to get a result while antigen testing can produce results with limited materials in less than an hour.
PCR sample collections can be done at home but have to be sent to a lab for results. Rapid antigen tests can be done completely at home. It's possible to get PCR test results in a few hours if you have direct access to a lab and there is no one else waiting.
However, as this scenario is unlikely, a rapid antigen test will almost always provide faster results. That said, the PCR test will still produce more accurate results.
If you get a positive COVID test result—no matter which test you use—you should stay home and isolate. Generally, you are contagious for about 10 days after you are infected with the virus. Call your healthcare provider if you have questions about testing, quarantine, or treatment. You can help prevent the spread of COVID by getting tested if you have symptoms, staying home if you are sick, isolating yourself from others as you quarantine, practicing frequent handwashing, and wearing a face mask.
Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Centers for Disease Control and Prevention. Updated November 23, Updated August 7, February ;n doi Hafer N. Updated November 9, Updated April 21, Updated December 15, Infectious Diseases Society of America.
Rapid testing. Updated October 25, When you visit this site, it may store or retrieve information on your browser, mostly in the form of cookies. Cookies collect information about your preferences and your device and are used to make the site work as you expect it to, to understand how you interact with the site, and to show advertisements that are targeted to your interests.
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Ronald Lubelchek, MD. Medically reviewed by Ronald Lubelchek, MD. Learn about our Medical Expert Board. Table of Contents View All. Table of Contents. PCR Test. Rapid Test. Choosing a Test. Frequently Asked Questions. When you get the kit or arrive at your testing center, you or a technician will insert a testing swab into your nose.
If you are doing the swabbing, you will be instructed how far to insert the swab into your nose and how many swipes to take inside each side of your nose. Usually, you will swab each nostril with the same swab for the best results. When the test is done, you will go home or send in your test kit and wait for the results. How long it takes will depend on the lab or service that you use and the demand in your area. It typically takes several days to receive results from a PCR test—or several hours at minimum.
Cons Can be too sensitive e. Rapid Antigen COVID Testing The first step in getting a rapid antigen test is to order your test kit online or pick it up from a store or healthcare office. When you open the kit, read the instructions carefully. Each manufacturer may have different instructions to follow.
In most cases, the kit will include a liquid, a swab, and a container or holder to put the swab in while you wait for the test results. For the next step, you will usually be instructed to wet the testing area with a liquid that comes with the kit.
You will then use the enclosed swab to collect your sample. This typically involves circling the swab several times in each of your nostrils. Once you are done swabbing, you will place the swab onto or into the test kit as instructed. The swab will begin producing a result when it reacts with the testing surface and liquid. While you may see results almost immediately in the form of a colored line or another sign, wait until the instructed time to confirm your results. Many tests state results are reliable in 15—30 minutes.
Cons Less accurate than PCR Does not work as well if you have no symptoms Accuracy depends on the quality of the sample you collect User error can affect results.
How are PCR and antigen tests different? Which test will give me quicker results?
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