COVID-19 virus test

Definition

To test for the virus that causes COVID-19, a health care provider will take a mucus sample from your upper respiratory tract. This test is used to diagnose COVID-19.

The COVID-19 virus test is not used to test your immunity to COVID-19. To test if you have antibodies against the SARS CoV-2 virus, you need a COVID-19 antibody test.

Alternative Names

COVID 19 - Nasopharyngeal swab; SARS CoV-2 test

How the Test is Performed

You will be asked to cough before the test begins and then tilt your head back slightly. A sterile, cotton-tipped swab is gently passed through a nostril and into the nasopharynx. This is the uppermost part of the throat, behind the nose. The swab is left in place for several seconds, rotated, and removed.

There are two types of virus tests available that can diagnose COVID-19:

• Polymerase chain reaction (PCR) tests detect the genetic material of the virus that causes COVID-19. The samples  are usually sent to a laboratory for testing, and results are available in a few days. There are also rapid PCR diagnostic tests that are run on specialized equipment on-site, for which the results are available immediately.
• Antigen tests detect specific proteins on the virus that causes COVID-19. Antigen tests are rapid diagnostic tests, which means the samples are tested on-site, and results are available in several minutes.
• Rapid diagnostic tests of any kind are less accurate than the regular PCR test. If you get a negative result on a rapid test, but have symptoms of COVID-19, your provider may do a non-rapid PCR test.

If you have a cough that produces phlegm, the provider may also collect a sputum sample. Sometimes, secretions from your lower respiratory tract can also be used to test for the virus that causes COVID-19.

How to Prepare for the Test

No special preparation is needed.

How the Test will Feel

You may have slight or moderate discomfort and may gag.

Why the Test is Performed

The test identifies the SARS-CoV-2 virus (severe acute respiratory syndrome coronavirus 2), which causes COVID-19.

Normal Results

The test is considered normal when it is negative. A negative test means that at the time you were tested, you probably didn't have the virus that causes COVID-19 in your respiratory tract. But you can test negative if you were tested too early after infection for COVID-19 to be detected. And you can have a positive test later if you are exposed to the virus after you were tested.

For this reason, if you have symptoms of COVID-19 or you are at risk for contracting COVID-19, your provider may recommend being retested at a later time.

What Abnormal Results Mean

A positive test means that you are infected with SARS-CoV-2. You may or may not have symptoms of COVID-19, the illness caused by the virus. Whether you have symptoms or not, you can still spread the illness to others. You should isolate yourself in your home and learn how to protect others from developing COVID-19. You should stay at home and away from others until you meet the guidelines for ending home isolation.

References

Centers for Disease Control and Prevention website. Coronavirus disease 2019 (COVID-19). Overview of testing for SARS-CoV-2. www.cdc.gov/coronavirus/2019-ncov/hcp/testing-overview.html. Updated July 17, 2020. Accessed July 22, 2020.

Centers for Disease Control and Prevention website. Interim guidelines for collecting, handling, and testing clinical specimens from persons for COVID-19. www.cdc.gov/coronavirus/2019-ncov/lab/guidelines-clinical-specimens.html. Updated July 8, 2020. Accessed July 22, 2020.

Kucirka LM, Lauer SA, Laeyendecker O, Boon D, Lessler J. Variation in false-negative rate of reverse transcriptase polymerase chain reaction-based SARS-CoV-2 tests by time since exposure [published online ahead of print, 2020 May 13]. Ann Intern Med. 2020;M20-1495. PMID: 32422057 pubmed.ncbi.nlm.nih.gov/32422057/.