WIDESPREAD rapid antigen testing of asymptomatic people will be key to relieving pressure on NSW’s overwhelmed SARS-CoV-2 testing and tracing systems, experts say.

NSW Health announced on Friday that all authorised workers who work outside their Local Government Area (LGA) of concern would only be permitted to work if rapid antigen testing was implemented at their worksite or if they had their first vaccination dose by 30 August.

Rapid antigen tests are already being used by some Australian employers, including Opera Australia and Fortescue Metals. Several nursing homes are also part of a Federal Government trial.

However Australia has been slower to embrace the technology than other countries, including the UK, where the Johnson government has spent billions of pounds on home test kits it doesn’t know whether people are using.

University of New South Wales epidemiologist and World Health Organization adviser, Professor Mary-Louise McLaws told InSight+:

“The best rapid tests, used preferably on the same group of people several times a week, perform brilliantly as a screening test for workers in the asymptomatic period.”

“There has been a reluctance to roll these tests out, I think because people don’t appreciate that this is a screening test rather than a diagnostic test,” Professor McLaws said. “Outbreak management using these tests is not the same as providing a diagnostic service.”

“I’m not suggesting that you’d use this for a once-off test, but it should be being used regularly for essential service workers, who haven’t been able to be fully vaccinated, so we know they’re safely negative.”

“This should have been rolled out months ago,” she added.

Professor McLlaws likened the job of NSW contract tracers of Delta to “chasing a racehorse on foot”.

“They just can’t keep up,” Professor McLaws told InSight+.

Professor Allan Saul, Senior Principal Research Fellow (Honorary) at Melbourne’s Burnet Institute said the fact there were hundreds of cases “under investigation” in NSW each day suggested “a major problem in contract tracing”.

“At this rate, there will be many thousands of cases daily by the time we get to 80% double vaccine coverage,” he said. “There is no way the contact tracing can keep up with this number, but for the vaccine rollout to be effective, it needs efficient contact tracing.

“Rapid diagnostic testing will add a negligible number of people in quarantine compared to the current testing, but has the possibility that asymptomatic people will be found that would be missed by current testing, and a lot of true negatives won’t clog up the testing and have to go into isolation for 1-2 days.”

Australia’s Therapeutic Goods Administration has approved 21 rapid antigen tests (lateral flow tests) for use in pathology laboratories or by health professionals at the point of care. Using a nasal swab, these tests can provide results within 15 minutes compared with 1–3 days wait for laboratory results with the gold-standard polymerase chain reaction (PCR) test.

Accuracy (sensitivity and specificity) varies between tests, and is highest in the first few days of symptom onset, when viral load is highest. A Cochrane review published in March found the tests correctly identified infection in 29-85% of asymptomatic people.

However, Professor McLaws noted this review included tests with a range of sensitivity rather than only those with at least 98%.

According to the Cochrane review test accuracy vastly improves when the tests are repeated several times a week.

A recent study of 43 US college students who had either tested positive or were a close contact found rapid antigen tests were as accurate as PCR when done every three days (98% sensitivity).

Dean Whiting, CEO of Pathology Technology Australia estimated that around 3000 COVID-19 rapid antigen tests are currently being performed in Australia daily across around 40 commercial and entertainment organisations.

“NSW Health is piloting a process for rapid testing on some building sites and manufacturing sites,” he said. “The missing link is the software to automatically link test results with medical records, but that’s now very close – probably we’ll have it within a month.”

“The TGA will need to consider modifying the use conditions so that self-collection and self-testing can be done on a worksite, with a health practitioner supervising groups of workers as they arrive for the day.”

Of all the rapid tests performed in Australia to date, Mr Whiting said there had been no true positives to his knowledge.

“This is consistent with a rule-out test,” he said. “Rapid antigen testing is for repeat testing of at-risk asymptomatic cohorts. That means people in essential services, food processing, distribution and transport services, hotel quarantine, COVID wards and aged care.”

“This kind of testing could stop lower-risk people joining those really long queues and taking up valuable resources in the laboratories,” he added.

Associate Professor David Anderson, Chief Scientific Officer, Burnet Diagnostics Initiative, said rapid antigen tests could improve capacity in Australia’s testing and tracing systems, but should be rolled out systematically and carefully.

“A massive rollout of antigen testing without the right structures in place could give a false sense of security,” he said.

“The very high transmission of Delta within households is an important factor,” he said. “If a high-risk worker has a false negative result, then if there is workplace transmission, their co-workers will be picked up within a couple of rounds.”

“But if there is no transmission at work and their family are not symptomatic or not screened, there can be undetected chains of transmission until the next time it either makes someone symptomatic, or infects another essential worker who gets screened,” he said.

False positives could also present a major problem, he said, unless sites doing rapid antigen testing had access to extremely rapid confirmatory PCR testing. Point-of-care PCR systems are available which can provide COVID test results within an hour, he noted. Longreach Hospital last year spent $32,000 on one such system.

Professor McLaws agreed that rapid PCR confirmatory testing was essential, but said that shouldn’t be a barrier to widespread rollout.

“Governments can mandate that if you’re going to use rapid antigen testing in the workplace, it’s beholden on the workplace safety officer to notify the department of health as soon as there is a positive case, so that it can be rapidly verified with PCR, and then the contact tracing can start,” Professor McLaws said.

Mr Whiting said that, at the Howard Springs quarantine facility in Darwin, over 30 000 tests were performed on staff over 7 months, with only 3 false positives.

“You put the positive case into isolation, do the PCR and do not initiate contact tracing until you have a positive result,” he said.

Mr Whiting said rapid antigen testing was likely to become essential once the 80% vaccination milestone is met.

“We know from Israel, where vaccination rates were very high, very quickly, now breakthrough infections are quite a problem,” he said. “Rapid testing – and increasingly in the UK and Europe, home testing – has become a standard public health tool to minimise people moving through the community when they’re infectious.”

“The sooner we get used to this idea, the better, because COVID-19 won’t be the last respiratory pandemic that we face.”

A Department of Health spokesperson told InSight+ the government’s position on allowing access to self-testing “will continue to be monitored”.

“But at this point in time, COVID-19 self-tests cannot be supplied in Australia,” the spokesperson said.

“Rapid antigen tests for self-testing in the future is critically dependent on achieving the vaccination rates as outlined in the National Plan to Australia’s COVID-19 response, and consideration as to what system of reporting and recording of rapid antigen self-test results is needed,” they added.

 


Poll

Rapid antigen testing for asymptomatic people should be made available to the public
  • Strongly agree (71%, 159 Votes)
  • Agree (17%, 39 Votes)
  • Disagree (5%, 12 Votes)
  • Neutral (4%, 8 Votes)
  • Strongly disagree (3%, 7 Votes)

Total Voters: 225

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16 thoughts on “Rapid antigen testing key for asymptomatic screening

  1. Anonymous says:

    “They are not sensitive enough and will give false negatives.” You know what gives even more false negatives? Not testing at all, which is the alternative in the proposed cohorts.

  2. Anonymous says:

    Dear Anonymous cardiologist, see:

    – NSW Health site: https://www.nsw.gov.au/covid-19/health-and-wellbeing/rapid-antigen-testing
    – TGA website:
    * https://www.tga.gov.au/qas-conditions-supply-rapid-antigen-tests (FAQ)
    * https://www.tga.gov.au/resource/covid-19-rapid-antigen-tests-guidance-and-checklist-businesses (advice for businesses)
    * https://www.tga.gov.au/covid-19-test-kits-included-artg-legal-supply-australia (list of approved tests)

    I can’t vouch for any individual tests except to say that the Abbott Panbio and Access CareStart are being used at a range of sites in Sydney.

  3. Anonymous says:

    The point of emphasis here is that rapid antigen testing is for screening a low risk population and not for diagnosing patients with clinical symptoms or epidemiological risks. The idea is that we can serially screen the same asymptomatic population who otherwise would not be tested. This test cannot be compared with a PCR which is reserved for symptomatic or high-risk people, or for those who are about to undergo a specific one-off event such as surgery. We are not comparing apples with apples. The test simply works as a bit of a safety net to detect positive cases that would otherwise have gone undetected for much longer.

  4. Bill Fleming says:

    Hang on ,I’ve just realised this article is out of date…the NSW government changed their mind after all these businesses have spent a lot of money getting ready and dropped the rapid antigen testing option…great ….are we ever going to get this wonderful tool to reduce numbers organised in Australia…we are so inept

  5. Bill Fleming says:

    If testing a targeted at risk population regularly such as an area showing a positive wastewater result..any false negatives will be caught very quickly on the next round ! I have been begging for the introduction of these screening tests for months while both the prime minister an d’y he Victorian CHO have denied their value . I truly believe we could have killed this Victorian outbreak…maybe still can .

  6. Anonymous says:

    Doesn’t make sense – 3 rapids several times a week = 1 week before you know if you are true positive or true negative vs 1 PCR = within 24 hrs know positive/negative with ~95% certainty.

    Could Prof McLaws outline an algorithm of how she proposes to use RATs?

    One these are floated in the market, people will ‘misuse’ them to ‘clear’ themselves as they wish. How do you control this?

  7. Anonymous says:

    Best use of rapid antigen tests is in people who we currently allow to behave as “presumed negative” eg those who are considered essential workers or drivers, school attendees etc. The argument of false neg / pos rates is meaningless in populations we don’t currently test because we don’t screen. So essentially we treat these as negative. To reduce this from 100% to 2% false negative is an added level of safety we don’t currently have in Australia due to the fallacy of ‘inaccuracy’ of screening test against a diagnostic test unfortunately.

  8. Anonymous says:

    well please look at Asian mode who had experience in last SAR out break. It was magically disappeared. They have been using this test for ages. Please it is time Australian should not be behind. There are plenty of example in Asian neighbouring countries.

  9. Anonymous says:

    A false negative doesn’t excuse you from wearing a mask etc, as it is not perfect, but if the test picks up +ve cases , in asymptomatic people ,its a definite worth it

  10. Anonymous says:

    They are not sensitive enough and will give false negatives. Biology 101. Yes, I am an expert in the science, manufacture and clinical utility of such tests. Ask any qualified scientist that has no financial gain from the approval of such devices. End of story

  11. Anonymous says:

    To the comment ” Too many false positives and negatives I hear”, a small study funded by NIH has found that COVID-19 antigen testing and PCR tests are equally effective in detecting SARS-CoV-2 infection when used for serial screening conducted every three days.

  12. Dr Michael Cejnar says:

    If you look up these distributors:
    Ape medical
    Arista – Health Vision
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    OnSiteDrugTesting

    or contact me at Micropace

  13. Greg Heron says:

    You can order them through your local PHN

  14. CC says:

    too many false positives and false negatives I hear.
    imagine telling someone that the test result is negative when in actual fact they do have covid and then watching them spread it to lots of people.

  15. Anonymous says:

    RAT testing is the most plainly obvious way to combat the pandemic properly. The sooner a public framework is set up the better. Professionals will always have their doubts, but in the meantime case numbers are rising and an opportunity to go hard on covid testing is still around…

  16. Anonymous says:

    As a cardiologist, I continue to deliver face to face care in private practice and hospital. In private practice, a point of care rapid Covid test would significantly increase the safety of the staff when patients need a procedure like an echo or exercise stress echocardiogram.
    How can I access rapid antigen test kits?

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