In the AFR today:

Rapid antigen tests slow to catch on here

Research

Jill Margo
Health editor

Dominic Dwyer: Ultra-sensitive.

Calls are growing for Australia to follow the US and use rapid antigen tests to help control the pandemic, but local authorities are still testing the test.

They say while the principle of rapid antigen testing is sound, they are not as sensitive as the gold-standard swab tests and slow in high-volume situations.

When used at home or in a workplace, authorities worry the tests have the potential to disrupt the public health notification system.

Who can be sure results from an overthe-counter test will always be reported and, if they are not, will people know what to do in light of their results so they do not put others at risk?

While Australia aggressively follows each positive case, in the US cases are often not followed up because the country is overwhelmed with infection.

A number of the rapid antigen tests, which have received Emergency Use Authorisation by the US Food and Drug Administration, are now included on Australia’s Register of Therapeutic Goods for potential use here.

Dominic Dwyer, NSW director of Public Health Pathology, says there has been pressure from all quarters to use the rapid tests. His department is evaluating nine of them in a trial being conducted at Sydney’s Westmead Hospital by health body the Institute of Clinical Pathology and Medical Research.

‘‘Just because people read about what’s happening overseas doesn’t mean it applies here, where disease prevalence is so different. We want to be ultrasensitive with our testing and have the maximum public health response to any positive test,’’ he said.

Apart from sewage monitoring, three basic tests are used for COVID-19. The gold standard swab is a molecular test that detects the RNA of the virus.

If necessary, fast-tracked versions of it can produce results in two hours. Fast trackinghappensinhospitalemergencies, when patients are very ill, and was recently employed to test NSW Premier Gladys Berejiklian.

Second are the antibody tests that do not detect if a person is infected but look for antibodies to determine if they were infected in the past.

Laboratory-based antibody blood tests are reliable and have been used to track where the virus has been. An exercise in Sydney revealed that during the first wave more than 5000 infected people went undetected. But early in the pandemic millions of cheap, home antibody kits, requiring a finger prick, were imported into Australia. Although some had approval from the FDA, none were approved here.

‘‘The FDA has since gone backwards and revised some approvals for these antibody tests and for rapid antigen tests, because they were poor quality,’’ Professor Dwyer said.

Third, the rapid antigen tests use swabs to detect proteins of the virus. They have value if used repeatedly, such as daily testing of quarantine staff.

‘‘The test is not so sensitive, but if you’re testing people every day, you are going to capture anyone who has the disease. But if you test them once, you will miss cases,’’ Professor Dwyer said.

‘‘With a standard swab test, we can get through 20,000 or 30,000 tests a day, and get results out within a day or so. Rapid antigen tests take about 15 minutes per individual. So if 300 people want to board a plane, or disembark, you could only test 20 of them an hour. It would take an enormous amount of people and time to test high volumes of passengers moving through airports.’’

He said the tests were 70 to 80 per cent as sensitive as the gold standard test and the belief they were entirely reliable when they produced a negative result was wrong.