PCR and Molecular COVID-19 Testing
- Also Known As:
- Nucleic Acid Amplification Test (NAAT)
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Test Quick Guide
Molecular COVID-19 tests are designed to detect an active infection with SARS-CoV-2, the coronavirus that causes COVID-19.
The most well-known molecular test uses a laboratory method known as reverse transcription polymerase chain reaction (RT-PCR) that is often called PCR.
PCR and molecular tests work by looking for the virus’s genetic material in your test sample, which is usually taken by swabbing your nose or throat. Molecular tests analyzed by a laboratory are generally considered to be the most accurate method of diagnosing COVID-19.
About the Test
Purpose of the test
The purpose of PCR and other molecular tests is to determine if a person has an active infection of the coronavirus known as SARS-CoV-2. The test may be used for diagnosis, screening, and monitoring.
A molecular test is used for diagnosis when a person has signs or symptoms of COVID-19. It is used for screening in people who are asymptomatic but who may have had exposure to the virus, such as through close contact with an infected person.
In some cases, a laboratory-based molecular test is used to confirm the results of other types of tests. For example, a follow-up PCR analyzed by a laboratory may be used after a rapid test, at-home test, or COVID-19 antigen test.
What does the test measure?
Molecular tests are designed to detect the presence of SARS-CoV-2 by measuring very small amounts of the virus’s genetic material.
To conduct the test, genetic material is isolated from your test sample and then is copied many times. That genetic material can be analyzed for traces of SARS-CoV-2, and, because of the copying process, even small amounts can be detected.
Nucleic acids are the genetic material that is analyzed, and the copying process is known as amplification. For that reason, nucleic acid amplification testing (NAAT) is the technical name for this kind of molecular testing.
There are various types of laboratory methods to conduct this type of testing. RT-PCR has been commonly used in COVID-19 testing. Examples of other methods that may be used in NAAT include loop-mediated isothermal amplification (LAMP), transcription mediated amplification (TMA), nicking endonuclease amplification reaction (NEAR), strand displacement amplification (SDA), clustered regularly interspaced short palindromic repeats (CRISPR), and helicase-dependent amplification (HDA).
These types of laboratory techniques are not used exclusively for COVID-19. They can also be used to detect other kinds of viruses, and tests are available that can analyze the same test sample for SARS-CoV-2 as well as different strains of flu.
When should I get a PCR or molecular COVID-19 Test?
There are a range of different circumstances in which a molecular COVID-19 test can be appropriate.
If you have symptoms of COVID-19, a PCR test or other molecular test is regarded as the most reliable method to determine whether you have COVID-19. In these cases, the test is used in the process of diagnosis.
A molecular test can also be used for screening. If you have no symptoms, you may get a molecular test if:
- You have been in close contact with someone who has been diagnosed with COVID-19.
- You have been in situations at high risk of viral transmission, such as travel or large gatherings of people.
- You live or work in an environment like a correctional facility, nursing home, or homeless shelter where there is an elevated risk of viral spread or severe cases of COVID-19.
- You are going to have a medical procedure like a surgery or a procedure that generates tiny air particles known as aerosols.
- You are going to start taking a medication that affects your immune system.
- You are required to provide a negative test result by your employer, in order to travel, or to take part in another activity.
Because there are many different applications of molecular COVID-19 tests, your doctor can best explain whether this kind of testing is appropriate in your situation.
It is also important to note that who should get tested with a PCR or other molecular test can depend on available testing capacity in your area. When resources for testing are limited, certain uses of testing may be prioritized.
Finding a PCR or Other Molecular COVID-19 Test
How to get tested
Depending on your circumstances, there are different ways to get a PCR or other molecular test for COVID-19.
If you have symptoms of COVID-19, you should reach out to your doctor, and if symptoms are severe, you should go to the hospital or call emergency medical services. If you have symptoms, a doctor can prescribe diagnostic molecular
testing. Similarly, if you have tested positive on a rapid test, antigen test, or at-home test, you should contact your doctor who may choose to confirm that result with a PCR or molecular test.
In some cases, such as after a close contact with a person with COVID-19, a doctor may prescribe testing as a method of screening for SARS-CoV-2 infection even if you are asymptomatic.
If your doctor recommends a PCR test, they may either take the test sample in their office or refer you to another location, such as a laboratory or drive-through testing site, where a swab can be done in your nose or throat.
Not all PCR tests require a prescription. For many types of screening, you can contact a laboratory or health clinic directly for test options. Some molecular tests for COVID-19 have been developed as point-of-care tests, which means
that they can provide results without having to send your sample to a laboratory. These rapid tests as well as at-home tests may need confirmation with a repeat molecular test analyzed by a laboratory.
Can I take the test at home?
At-home PCR tests are available both with and without a prescription. At-home molecular COVID-19 tests generally fall within two categories:
- At-home self-collection tests: In these tests, you take a swab of your nose or throat or collect a saliva sample and send that sample by mail to a laboratory. Results are normally available within a few days after
your sample is received by the lab.
- At-home self-tests: These tests also involve taking your own test sample, but that sample is then analyzed at home using a device that is included in your test kit. These tests often provide results within 30
With either type of at-home test, it is essential to follow the test kit’s instructions for properly collecting your sample and avoiding potential sources of contamination.
While at-home tests are generally accurate, they are not considered to be as reliable as standard laboratory testing. Rapid tests are more susceptible to an inaccurate result than tests processed in a lab.
If you test positive, you should contact your doctor, who may want to perform a repeat PCR. You or your doctor may also need to contact your state health department that is responsible for tracking the number of COVID-19 cases.
How much does the test cost?
The cost of a PCR or other molecular test depends on where the sample is collected, how the sample is analyzed, whether the test is prescribed by a doctor, and whether you have health insurance.
Potential components of testing costs include office visits, technician fees for taking a nasal or throat swab, and charges for the molecular analysis by the laboratory. When prescribed by a doctor, most of these costs are covered by
insurance, but you may be charged a copay or deductible. In some cases, government programs are covering the full costs of COVID-19 testing.
At-home tests that are not prescribed by a doctor are not usually covered by insurance. At-home test options are often available for less than $150 per test.
Talk with your doctor and insurance provider to determine which test is most appropriate for you and what out-of-pocket costs you will be required to pay for testing.
Taking a Molecular COVID-19 Test
Molecular COVID-19 tests are typically conducted on samples collected from the respiratory tract. In most cases, the sample is taken with a swab of the nose or throat. Some tests can be done with a saliva sample.
Depending on the specific molecular test, the sample can be collected in many different places including a hospital, doctor’s office, health clinic, drive-through testing site, pharmacy, laboratory, or even at-home.
Before the test
No special steps are required to prepare for a molecular COVID-19 test.
For at-home tests, it is important to make sure that you follow any suggested steps to clean the area where you will prepare the test kit so that you can avoid contamination that might affect your test sample.
During the test
Your experience during the test can vary based on the type of sample required. Swabs may be needed from your nose or throat. To obtain the sample, a cotton swab is inserted into your nose or throat, left in place for a few seconds, and then turned a few times. A sample may be taken from both nostrils.
Some people find the procedure to be uncomfortable, especially if it requires inserting the swab deeper into your nostril to reach the nasopharynx, which is behind the nose. Your eyes may water, or the test may cause you to gag or flinch. The entire process is usually finished within minutes and normally does not cause any lasting pain.
Saliva can be used for certain molecular tests. This requires spitting into a tube until you have collected a sufficient amount of saliva.
After the test
Once your test sample is collected, you can leave the testing site and should not expect any side effects from the test.
While the test itself does not require any restrictions on activity, if you are being tested because of symptoms or potential exposure to the SARS-CoV-2 virus, you should follow appropriate precautions to prevent potential spread of the virus to others. This includes measures such as avoiding close contact with other people, avoiding large gatherings, wearing a mask, and washing your hands frequently.
PCR and Molecular COVID-19 Test Results
Receiving test results
If your test sample is sent to a laboratory to be analyzed, results are usually available in one to three business days. Turnaround time can depend on the demand for testing and available laboratory resources. You may get a phone call with your test result, or you may receive a test report either electronically or by mail.
Rapid PCR test options are available that can provide results in less than 30 minutes. These are also known as point-of-care tests because the sample is analyzed on-site and does not need to be sent to a laboratory. Some at-home tests are point-of-care options with rapid results.
Interpreting test results
The test result is generally listed as either positive or negative.
A positive result means that traces of SARS-CoV-2 virus genetic material were found in the test sample. This is sufficient to diagnose COVID-19 although you may not have any symptoms. If you test positive, it is essential to take steps to avoid spreading the virus to other people even if you don’t have any symptoms. Please speak with your physician and refer to the Centers for Disease Control and Prevention (CDC) guidelines for isolation and quarantine.
A negative test indicates that no genetic material of the virus was present in your sample. In most cases, this means that you do not have COVID-19. However, a false negative result can occur if testing is done shortly after being infected.
Your doctor is in the best position to review your test report and explain what it means for your health.
Are test results accurate?
While no test is 100% accurate, the PCR and other molecular tests are widely considered to be the most reliable method of diagnosing COVID-19.
Because the test can detect even very small amounts of the genetic material of SARS-CoV-2, it is rare for the test to come back positive if a person is not infected or has not recently been infected. A negative test result is usually accurate, but occasional false negative results have been reported in which the virus is not detected in a sample from a person who is infected.
Although these tests are typically very dependable, various factors can influence the accuracy of molecular testing. The part of the body where the sample is taken, proper specimen collection and handling, and the method of laboratory analysis may affect the test result.
Rapid, point-of-care tests are also usually reliable but may be less precise than laboratory analysis. For this reason, results from rapid PCR tests may be confirmed with repeat testing using laboratory methods.
Do I need follow-up tests?
In many cases, no follow-up testing is necessary after a molecular test. However, a second molecular test may be recommended if there are questions or doubts about your initial result. If you have symptoms, a wide range of other medical tests may be used to evaluate your condition. Your doctor is in the best position to describe if any type of follow-up tests are recommended in your situation.
Questions for your doctor about test results
The following questions may be helpful to bring up when you discuss your COVID-19 test result with your doctor:
- Which type of molecular test did I have, and how accurate is that testing method?
- Based on my test result, do I need to take any special precautions related to COVID-19?
- Is there any benefit to repeating the test?
- Are there other types of tests that might be helpful in my situation?
Distinct types of tests have been rapidly developed since the emergence of the coronavirus pandemic. Knowing the differences between them can help you understand the role that each type of test can play in medical care for COVID-19. The table below and the following sections explain the similarities and differences between available tests for COVID-19:
|PCR and Molecular Tests||Detect current infection||Nose swab, throat swab, or saliva sample|
|Antigen Test||Detect current infection||Nose swab|
|Antibody Test||Detect prior infection||Blood sample|
How is a PCR different from a COVID-19 antigen test?
Both PCR and antigen tests are methods of detecting an active infection of SARS-CoV-2, but they accomplish this in different ways.
Molecular tests like a PCR look for the genetic material of SARS-CoV-2. Antigen tests identify the presence of a particular kind of protein, known as an antigen, that is found on the exterior of the virus itself.
Both molecular tests and antigen tests can be conducted on a sample taken from your nose, but molecular tests can be performed on saliva or throat samples as well. Both types of tests can be analyzed either in a laboratory or with a rapid, point-of-care system.
In general, PCR tests are considered to be more accurate than antigen tests, and in some cases, a PCR is used to confirm the result of an antigen test.
How is a PCR different from a COVID-19 antibody test?
PCR and antibody tests have different purposes. A PCR is a way of looking for an active viral infection while an antibody test looks for signs of a past infection.
Antibodies are created by the immune system to help fight infections. It normally takes a few weeks for antibodies to develop after a person has been infected, so antibody testing is not useful for determining whether someone currently has COVID-19.
Other related tests
Sources and Resources
The following resources provide regularly updated information about the symptoms, prevention, and treatment of COVID-19:
- CDC: COVID-19
- National Library of Medicine: COVID-19
- World Health Organization: Coronavirus disease (COVID-19) advice for the public
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Centers for Disease Control and Prevention. Test for current infection (viral test). Updated March 18, 2021. Accessed April 22, 2021. https://www.cdc.gov/coronavirus/2019-ncov/testing/diagnostic-testing.html
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Palmore TN, Smith BA. COVID-19: Infection control in health care and home settings. In: Sexton DJ, ed. UpToDate. Updated April 16, 2021. Accessed April 22, 2021. https://www.uptodate.com/contents/covid-19-infection-control-in-health-care-and-home-settings
UpToDate. COVID-19: Questions and answers. Updated April 19, 2021. Accessed April 22, 2021. https://www.uptodate.com/contents/covid-19-questions-and-answers
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US Food and Drug Administration. Coronavirus (COVID-19) update: FDA authorizes first COVID-19 test for self-testing at home. Updated November 17, 2020. Accessed April 24, 2021. https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-first-covid-19-test-self-testing-home
US Food and Drug Administration. Coronavirus (COVID-19) update: FDA issues authorization for first molecular non-prescription, at-home test. Updated March 5, 2021. Accessed April 24, 2021. https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-issues-authorization-first-molecular-non-prescription-home-test
US Food and Drug Administration. Coronavirus (COVID-19) update: FDA issues emergency use authorization for the symbiotica COVID-19 self-collected antibody test system. Updated April 6, 2021. Accessed April 22, 2021. https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-issues-emergency-use-authorization-symbiotica-covid-19-self
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