Pathologists warn against rapid new test for 'early' COVID-19
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Jill MargoHealth Editor
Apr 2 2020
The new rapid blood test kits for COVID-19 are not reliable when testing for “early disease”, according to the Royal College of Pathologists of Australasia.
It says molecular laboratory testing using a swab in the throat and then deep in the nose is the current test of choice for the diagnosis of "acute" COVID 19 infection.
College president Dr Michael Dray says the rapid tests have a fundamental limitation. They rely on the detection of antibodies made by the patient in response to the virus and do not detect the virus itself.
Patients may only make antibodies a week to 12 days after they first become sick. “Therefore, if doctors rely on these rapid tests early in the disease, their diagnosis will be wrong.”
While the antibody tests should not be used to screen for early infection, he said they might have a place in detecting unrecognised past infection and immunity but that role still needed to be rigorously evaluated.
To date, Australia has been using the swab tests that can take days to return a result.
The pin-prick test kit, which is already being imported into Australia, works like a home pregnancy test and returns a result in 15 minutes, as the patient waits.
The college says the swab is the current test of choice and pin-prick tests “have no role to play in the acute diagnosis of COVID-19 virus infection”.
Last week one distributor of the rapid kits, MD Solutions, reported receiving fast-tracked approval from the Therapeutics Goods Administration to bring kits into Australia .
Its CEO, Xavier Lawrence, said the company agreed there were limitations but as swab tests were running out around the world, and as no others were readily available, rapid testing should be an option.
Dr Dray said the rapid tests risked missing patients in the early stages when they were infectious, giving them a false positive result and erroneously reassuring them.
Further, elderly or immuno-compromised patients might take longer to develop antibodies, and some might never develop them.
In contrast, molecular tests directly detected gene sequences of the virus in the early stages of infection when the patient was infectious.
In the early days of the pandemic, Australia rapidly developed and implemented robust national testing capacity through the Public Health Laboratory Network (PHLN).
Now testing is broadly available through hospital and private pathology providers.
“It is encouraging that further review and assessment of the antibody tests has been commissioned by the TGA, " said Dr Dray.
Mr Lawrence supports the TGA thoroughly reviewing all rapid tests. He said the market had been illegally flooded with substandard tests that were at best useless and at worst dangerous.
