Understanding COVID-19 Testing Technologies and Terminologies
By Eve Vickerson - AMWA Committee Member
Viral nucleic acid tests, antigen tests, antibody tests, T-cell analysis, serology, sequencing. Just a sample of the terms and tech that you need to understand when writing about COVID-19 testing. Understand them all? Good, but I’m now going to spring a quick test on you – just like your favourite high school teacher:
What does “PCR” stand for?
(a) Positive Chemical Reaction
(b) Polymerase Chain Reaction
(c) Photocopying Critical Reagents
(d) none of the above
Need to brush up on your testing knowledge? This webinar from AMWA’s series, The COVID-19 Vaccine – Your Questions Answered is for you.
Clinical biochemist and CEO of Pathology Technology Australia, Dean Whiting, outlines the key technologies and terminologies around detection and sequencing of the COVID-19 virus and why they’re important. Read on to find the answer to the PCR pop quiz and enjoy some of the highlights of this enlightening webinar.
The story begins with sequencing
At the presentation's start, Mr Whiting introduced sequencing technology and said that it was the beginning of the story for COVID-19 testing.
“There was very little we could do until the viral genome was sequenced. From sequencing, we were able to generate the reagents or the chemicals required to do PCR testing.”
For those of you playing at home, polymerase chain reaction (PCR) testing “is where you multiply up many, many millions of copies of the gene of interest or the segment of the gene of interest.”
While other nucleic acid tests are used for COVID-19 testing, Mr Whiting said that PCR is commonly thought of as the gold standard diagnostic test because it tends to be more accurate.
COVID-19 testing types explained
During his presentation, Mr Whiting described the following types of COVID-19 testing technologies:
Viral nucleic acid tests
In the case of SARS-CoV-2, PCR testing can be used to detect viral genetic material early after a person is exposed to the virus. It may also detect viral genetic material for a period of up to 8 weeks after exposure, even when a person is no longer infectious.
Mr Whiting said the pros of PCR testing are that it is sensitive, accurate, automated and capable of high throughput. But, he said it’s not perfect because:
- it involves complex technology
- can be expensive
- it takes 1-2 days to produce results
- has a relatively high false positive rate.
From time to time, people who are well past their infectious phase and don’t have a viral load capable of transmitting the disease test positive for COVID-19 based on PCR testing. However, as Mr Whiting said, “it’s hard to call this a false positive when you can actually measure a fragment of RNA. But in fact, it is a false positive because when you have very low levels of RNA, it’s not infectious.”
As Mr Whiting explained, antigens are the proteins produced by a contagion that elicit the antibody response. In the context of COVID-19, Mr White said that measuring antigens is quite important because they are a very early marker of infection.
According to Mr Whiting, rapid antigen tests are suitable for screening people in the first hours and days when they are most infectious. This type of testing is inexpensive, requires little to no equipment, produces results in 15–20 minutes and is highly accurate in the first 5–7 days.
However, Mr Whiting said that rapid antigen testing is not suitable for high volume testing or detecting COVID-19 after the first seven days.
While there were high hopes surrounding antibody testing early in the pandemic, Mr Whiting said that it turns out antibodies are not the best thing for diagnosing COVID-19 after all. Instead, he describes them as being more like rearview mirrors. “Antibodies are very good at saying if you have had an infection or potentially, whether your vaccination has been effective.”
Described by Mr Whiting as the “new kid on the block", T-cell tests were approved by the US Food and Drug Administration in March 2021 for COVID-19 testing. This type of testing involves sequencing the genomics of a T-cell to see if it switched on to attack SARS-CoV-2 cells.
According to Mr Whiting, T-cell testing will be very useful in detecting the long-term immune response to COVID-19, even after the initial antibodies have disappeared. “I suspect that as we go down the vaccination pathway, T-cells will be quite important because we don't know how long the antibodies will be measurable in blood. If we do find that there are still T-cells there, it means that people can still mount an immune response. But, it's still pretty early days.”
Sequencing has been used to detect COVID-19 variants and to identify people infected by the same strain of the virus. While it is highly accurate, Mr Whiting said that sequencing can also be time-consuming and is still relatively expensive.
How do we test the effectiveness of vaccines?
Mr Whiting said that the traditional methods of determining vaccine effectiveness involve antibody testing. This is often called seroconversion or serology testing. According to Mr Whiting, T-Cell analysis and sequencing may also be effective in testing how well vaccines are working.
What role will testing have in the new COVID normal?
At this point in the webinar, Mr Whiting gave a very helpful overview of how we will use testing technology after mass vaccinations have occurred. So, if you want to know what type of test might be best for screening inbound travellers (remember travel?) or what to use if antibody testing is indeterminant, take advantage of your AMWA membership now and watch the replay.
Passing the test
As well as being incredibly informative, this webinar helps you learn about COVID-19 testing technology in a way that’s both interesting and
easy to understand. Make sure you catch the replay, which is available to AMWA members here.
Oh, and if you missed the answer to the PCR pop quiz, it was (b) Polymerase Chain Reaction. You’re welcome.
Eve Vickerson is a health and medical writer based in Brisbane, Australia. She specialises in creating clear, caring and credible content for health consumers and healthcare providers.
Combining a master’s degree in marketing with her past experience as the marketing manager at a major hospital research foundation, Eve applies health-literacy strategies to produce thoroughly researched, up-to-date, evidence-based content. She also volunteers her time on the AMWA Executive Committee. You can connect with her on LinkedIn and Twitter.