- 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.
- 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.
How the test is performed:
- A fluid sample is collected by inserting a long nasal swab (nasopharyngeal swab) into your nostril and taking fluid from the back of your nose or by using a shorter nasal swab (mid-turbinate swab) to get a sample.
- In some cases, a long swab is inserted into the back of your throat (oropharyngeal swab), or you may spit into a tube to produce a saliva sample
- 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).
- 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.
- 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.
- 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.
Note : 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.
- Results interpretation
- 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.
- 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.