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GP issues warning over COVID testing confusion


Anastasia Tsirtsakis


24/03/2022 3:37:04 PM

Rapid antigen tests versus PCR – which is appropriate, and when? GPs are being urged to educate patients in the lead up to winter.

A women inserting a swab into her nose.
Prior to conducting a rapid antigen test, patients should be encouraged to read the instructions as products vary.

When it comes to testing for COVID-19, RACGP Victoria Chair Dr Anita Muñoz has noticed growing confusion among her patients.
 
She says it started to set in over the holiday period, when testing sites became overwhelmed with demand for PCR testing and there was a swift transition to rapid antigen tests.
 
‘I think what’s happened is that over time people have probably received mixed messages about PCR and the use of rapid antigen tests in the context of testing for COVID,’ Dr Muñoz told newsGP.
 
‘The messages have become blurred as a result of so much information entering the public arena … and so that has led to some of the tests being used and the interpretation of their results not accurately reflecting the situation for which the testing has been done.’
 
And the confusion isn’t just among patients. The Melbourne GP says she has noticed a similar lack of clarity among clinicians.
 
Dr Muñoz believes that the intended use of rapid antigen tests was not clearly outlined to ensure their optimum use, with people made to believe that they are the go-to option, and as accurate and valid as a PCR.
 
‘That is not correct,’ she said.
 
‘Tests have false positive and false negative rates that you have to take into account.
 
‘Now that’s not to disparage the test; rapid antigen tests have a very helpful role to play, provided that the person has an understanding of what to do with the results that they get based on the context of the testing.’
 
So, when is it appropriate to take a rapid antigen test result at face value – and when should further clarity be sought?
 
If patients have access, Dr Muñoz says rapid antigen tests are a great first step to determine whether someone may be COVID-positive.
 
This is particularly the case when an individual may be symptomatic, and returns a positive result, or is asymptomatic and receives a negative result.
 
In other scenarios, however, where the symptoms and the result do not match up, Dr Muñoz says there are nuances to consider.
 
‘If you have symptoms of COVID and the rapid antigen test is negative, you absolutely should go ahead and get the PCR done because the test may be giving you a false negative,’ she said.
 
‘And if you have no symptoms at all and it comes back positive – and you’ve done a rapid antigen test for compliance reasons – again, you should question the validity of the result. It may be a false positive, so you would also then do a PCR.’
 
As it stands, PCR tests are considered the gold standard when it comes to detecting COVID-19. They can detect the presence of nucleic acids, which is the genetic material of the virus, early in the infection, and sometimes even prior to symptoms developing.
 
Rapid antigen tests detect the presence of specific proteins of the virus, and are most accurate when used to test symptomatic individuals.
 
To ensure the test is as accurate as possible, Dr Muñoz said it is important that people are encouraged to read the individual instructions of the product they are using, as specifications can vary.

COVID-reminder-article.jpg
RACGP Victoria Chair Dr Anita Muñoz is concerned complacency around COVID-19 is setting in ahead of winter. 

While rapid antigen tests have proved to be a useful tool, what makes their predictive value complex is that their accuracy increases alongside the level of COVID infection circulating in the community.
 
Dr Muñoz says that this concept can be challenging for people to understand, as it can be ‘mathematically counterintuitive’.
 
‘It talks to whether a test has false positive and false negative rates, which is actually slightly different to the positive or negative predictive value of a test, which is something that changes depending on how common the illness is in the population that you’re screening,’ she said.
 
‘I don’t think it’s reasonable for us to explain that to the public or expect them to grasp that.
 
‘What we want is for them to be able to interpret their results based on the scenario of their testing and if the symptoms and the test don’t make sense, go ahead and still use the PCR.’
 
As the cooler months approach, Australian GPs are bracing for the first winter that international borders will be open since the COVID-19 pandemic was declared more than two years ago.
 
While national vaccination rates are some of the highest in the world, booster uptake is lagging, as is interest from parents of children aged under 11, and with rising prevalence of the highly infectious Omicron subvariant BA.2, new daily infections are once again starting to be recorded in the tens of thousands.
 
A compounding factor is that most states and territories having eased public health measures, with an expected return of influenza and other respiratory diseases flagged.
 
Dr Muñoz says she is concerned that fatigue among the community over COVID-19 will lead to rising levels of complacency.
 
‘There is a false assurance that is settling into the community that the pandemic is over because the visibility of those statistics has been obscured by the media moving on to other important world events, like the war in Ukraine,’ she said.
 
‘But the numbers are still there; we’re still getting thousands of cases a day, we’ve still got people in ICU and people are dying every day.
 
‘So we’ve got to resist the urge to be falsely reassured.’
 
Dr Muñoz says this also goes for influenza, which she senses many think has become redundant, despite modelling predicting that it will likely be more virulent.
 
She says this is where the ability to distinguish between COVID and other respiratory antigens will become increasingly important, and noted that GPs have an increasingly important role to educate patients about testing.
 
‘Rapid antigen tests will be a big part of our testing strategy in winter, so it’s going to be very important that we make sure that people use tests appropriately,’ Dr Muñoz said.
 
‘But if we have somebody who has COVID-like symptoms and a negative rapid antigen test, it would be really helpful for us to get them a PCR because we can also test them at the same time for things like influenza, so that we can understand epidemiologically what is happening in the community.’
 
The Melbourne GP acknowledged that while COVID fatigue is present in the community – and among clinicians themselves – ‘we can’t wish away our reality’.
 
‘I would much prefer to see people persevere with the minor inconvenience … than have to endure the huge and life threatening inconvenience of intubation, for example,’ Dr Muñoz said.
 
‘We can use our citizenship and own initiative to continue to protect ourselves and the people around us.’
 
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Dr Samantha Ann Bryant   25/03/2022 7:25:09 AM

It would be great if the health/ pathology services get on board doing pcr for covid and influenza together with winter and influenza season approaching. Could the RACGP advocate for this?