PCR Test

Posted September 30, 2022 by Anusha ‐ 3 min read

The nose swab PCR test for COVID-19 is an accurate and reliable test for diagnosing COVID-19. A positive test means you likely have COVID-19. A negative test means you probably did not have COVID-19 at the time of the test.

What is a PCR test?

  • PCR means polymerase chain reaction.

  • It’s a test to detect genetic material from a specific organism, such as a virus.

  • The test detects the presence of a virus if you have the virus at the time of the test.

  • The test could also detect fragments of the virus even after you are no longer infected.

What is a COVID-19 PCR test?

  • The polymerase chain reaction (PCR) test for COVID-19 is a molecular test that analyzes your upper respiratory specimen, looking for genetic material (ribonucleic acid or RNA) of SARS-CoV-2, the virus that causes COVID-19.

  • Scientists use the PCR technology to amplify small amounts of RNA from specimens into deoxyribonucleic acid (DNA), which is replicated until SARS-CoV-2 is detectable if present.

  • The PCR test has been the gold standard test for diagnosing COVID-19 since authorized for use in February 2020.

  • It’s accurate and reliable.

Who should get tested for COVID-19?

Your healthcare provider may recommend testing for COVID-19 if you have any of the following symptoms:

  • Fever or chills.

  • Cough.

  • Shortness of breath or difficulty breathing.

  • Fatigue.

  • Muscle or body aches.

  • Headache.

  • New loss of taste or smell.

  • Sore throat.

  • Congestion or runny nose.

  • Nausea or vomiting.

  • Diarrhea.

Procedure of PCR test

There are three key steps to the COVID-19 PCR test:

Sample collection

  • A healthcare provider uses a swab to collect respiratory material found in your nose.

  • A swab is a soft tip on a long, flexible stick that goes into your nose.

  • There are different types of nose swabs, including nasal swabs that collect a sample immediately inside your nostrils and nasopharyngeal swabs that go further into the nasal cavity for collection.

  • Either type of swab is sufficient for collecting material for the COVID-19 PCR test.

  • After collection, the swab is sealed in a tube and then sent to a laboratory.


When a laboratory scientist receives the sample, they isolate (extract) genetic material from the rest of the material in the sample.


  • The PCR step then uses special chemicals and enzymes and a PCR machine called a thermal cycler.

  • Each heating and cooling cycle increases (amplifies) the amount of the targeted genetic material in the test tube.

  • After many cycles, millions of copies of a small portion of the SARS-CoV-2 virus’s genetic material are present in the test tube.

  • One of the chemicals in the tube produces a fluorescent light if SARS-CoV-2 is present in the sample.

  • Once amplified enough, the PCR machine can detect this signal.

  • Scientists use special software to interpret the signal as a positive test result.

What do COVID-19 PCR test results mean?

Positive test result

  • A positive test result means that it’s likely that you have an infection with SARS-CoV-2.

  • This could be due to asymptomatic infection, but if you have symptoms, then this infection is called COVID-19.

  • Most people have mild illness and can recover safely at home without medical care.

  • Contact your healthcare provider if your symptoms get worse or if you have questions or concerns.

Negative test result

  • A negative test result means you probably didn’t have an infection with SARS-CoV-2 at the time your specimen was collected.

  • However, it’s possible to have COVID-19 but not have the virus detected by the test.

  • For example, this may happen if you recently became infected but you don’t have symptoms yet or it could happen if you’ve had COVID-19 for more than a week before being tested.

  • A negative test doesn’t mean you are safe for any length of time: You can be exposed to COVID-19 after your test, get infected and spread the SARS-Cov-2 virus to others.

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