Efficacy of COVID-19 RATs not reliable, say researchers

MedTech News: Researchers are calling for an overhaul of COVID-19 Rapid Antigen Tests (RATs). In a world first, researchers have developed a new way to rate the effectiveness of RATs, which would lead to more reliable testing of patients.

The James Cook University (JCU) study highlights the wildly varying accuracy of RATs and has prompted calls by the JCU team and others for better quality assurance of the tests.

JCU researchers used a fluorescent protein to develop a new reference standard to check RAT performance.

10 RATs were selected by the team for evaluation, who used a COVID-19 fluorescent protein to determine the lowest detectable amount of COVID-19 protein for each test. Out of the 10 RATs analysed, only two returned consistently positive readings at the lowest concentration of COVID-19 protein used.

While a recent Canadian study proposed a reference standard for RATs, JCU Associate Professor of Molecular and Cell Biology Patrick Schaeffer said the JCU study was the first of its kind to not only develop a standard but implement it to compare RATs.

“This reference standard has allowed us to make very simple and efficient quality control assessments,” he said.

“At the moment, RAT performance is based on what the manufacturer says but they have never been compared using the same standardised COVID-19 protein.

“Currently, the Therapeutic Goods Administration (TGA) and World Health Organisation (WHO) request that manufacturers disclose the analytical sensitivity of their RATs but they are not cross-checked in an independent lab.”

The TGA said it is aware of commentary from James Cook University academics stating “We need to have a clean up of the RAT tests that are currently available” and “The RAT tests that are available were not cross compared independently because they were released in an Emergency Act”.  

In a statement the regulator said “Firstly, all COVID-19 RAT tests on the Australian market have been through the normal stringent processes of full TGA approval – they were not released in an Emergency Act. Secondly, in addition to in depth evaluation of submitted data by TGA scientists, independent assessment of approved RATs in collaboration with the Peter Doherty Institute for Infection and Immunity and the National (Serology) Reference Laboratory confirmed that RATs approved for use in Australia met global standards for sensitivity as set by the World Health Organisation (WHO) guidelines.“

The regulator argued that studies on 91 tests showed that only three RATs did not comply with the minimum requirements and these tests have been removed from supply in the Australian market. Results from the comprehensive validation testing, as they are finalised, are made public on the TGA’s website.  This means consumers can be assured that if used correctly, RATs continue to be an important part of detecting and managing COVID-19 infections. Members of the public are encouraged to refer to the TGA for accurate information about therapeutic goods approved for supply in Australia.

Associate Prof Schaeffer said the James Cook University results highlighted an urgent need for the TGA and WHO to push for a standard reference material to compare the accuracy of hundreds of different RAT brands.

“We need a reliable reference standard to rank all current and future RAT devices and ensure that their performance is accurately communicated to healthcare providers and the public,” he said.

“We believe our fluorescent nucleocapsid protein is a promising candidate for this task and will ensure that RAT performance is accurately communicated to healthcare providers and the public.

“At the moment, these RATs are assessed using viral cultures, without knowing the actual concentration of the COVID-19 protein. It’s like counting the number of mature trees in a forest and using that to determine the number of seeds sown. It depends on factors like soil quality and the viability of the seeds.”

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