Zeroing in on COVID-19 testing

Coronavirus has dominated the news globally over the past few months. Subsequently, there has also been a lot of talk about the different types of COVID-19 tests available. So, what are they and what’s so different about each one?

Diagnostic or PCR Testing

What is it and when should it be done?

A PCR (polymerase chain reaction) test directly detects the presence of viral RNA (genetic material) within the body. It is performed within the first 10 days of the onset of symptoms but is most reliable when performed within the first week of infection when antigen rates within the body increase due to the presence of the virus.

How is it done and how long will it take for results to come in?

The test analyzes a sample of mucous taken with the help of a nasopharangeal swab (a long Q-tip shaped device used to collect mucous from the back of the nasal cavity). While results are usually available on the same day, some locations take up to a week to deliver results based on how many samples they have collected.

What are the advantages and disadvantages of this test?

PCR or diagnostic tests are known to have high sensitivity as well as specificity and can be used to accurately determine who has an active COVID-19 infection or people who are contagious to others. However, results may sometimes take up to a week given the large number of such tests being performed due to the pandemic.  It also can’t detect if a person has been infected with COVID-19 in the past.

Antigen Testing

What is it and when should it be done?

Antigen testing is a rapid diagnostic test that detects an active virus by looking for the presence of specific proteins on the surface of the virus as opposed to viral genetic material. It can be performed 1 to 10 days from the onset of symptoms but like PCR testing, it is most reliable when performed within the first seven days of infection.

How is it done and how long will it take for results to come in?

Like PCR tests, Antigen tests also analyze mucous collected with the help of  a nasopharangeal swab. These tests provide results in as fast as 15 minutes’ time. 

What are the advantages and disadvantages of this test?

The test can be used to determine who has an active virus. Being quicker and comparatively cheaper than a PCR test, it can be used to screen people in hospitals or workplaces where it’s important to quickly find out if someone is currently at risk of spreading the disease. However, it is less sensitive than a PCR test and is unable to determine if a person has had COVID-19 in the past.

Antibody Testing

What is it and when should it be done?

An antibody test is a serological (blood) test that looks for the presence of antibodies to the coronavirus. These antibodies are produced as an immune response to an infectious agent after about 4 to 7 days. This test can be used after 7 to 10 days of COVID-19 symptoms. 

How is it done and how long will it take for results to come in?

For this, a blood sample is drawn and then analyzed on-site or sent to a lab for testing. Results often come in within an hour to a day depending upon the location and testing facility.

What are the advantages and disadvantages of this test?

The test can identify people who have been infected in the past. In some instances, it can also determine when the virus was contracted. As a consequence of this, it can qualify people to donate blood with the presence of these antibodies as a treatment for others. On the flip side, the test does not detect the antigen and is unable to detect antibodies if tested too early. Another factor to consider is that research is still trying to establish for how long these antibodies remain in the system.

If adequately deployed, diagnostic tests such as PCR and antigen testing can be effective to detect the presence of, and stop the spread of, the COVID-19 virus. On the other hand, antibody testing will play an essential role in determining any immunity that develops among a population. 

We hope this helps clarify the basics of all these essential COVID-19 tests. You can see all this information laid out in an easy to read infographic from Verify Diagnostics here!

Leave a Reply

Your email address will not be published. Required fields are marked *

seven + 10 =