Rapid PCR test just as good as standard nasal swabs

Embargoed until: Publicly released: 2021-11-26 00:01

New Zealand

PHOTO: Mufid Majnun/Unsplash

Kiwi researchers have tested out different kinds of rapid Covid-19 tests to assess how well they’d fare compared to our current testing methods. The team found that a rapid PCR test that takes 20 minutes to deliver results was just as sensitive as the gold standard nose swab currently used in New Zealand, whereas the rapid antigen tests they analysed didn’t work as well. The team says the drawback to this rapid PCR test is that only one sample can be tested at a time and that machines needed for this test cost more than $10,000 a pop, but the simplicity, speed and portability of the test would suit remote settings when quick results are needed.

Media release

From: New Zealand Medical Association (NZMA)

PCR is the current gold standard for detecting the COVID-19 virus. It is a type of nucleic acid amplification test (NAAT), which is a diagnostic technique that works by identifying the genetic material of the virus. Other testing methods include isothermal NAATs, which are similar to PCR tests but use a slightly different technology to identify the genetic material, and rapid antigen tests (RATs), which work by looking for proteins on the surface of the virus. RATs are less expensive than NAATs and operate in a manner similar to that of a home pregnancy test. Standard PCR tests within the laboratory take a number of hours to provide a result. Our study looked at the performance of three rapid NAATs (one rapid PCR and two rapid isothermal NAATs) and five brands of RAT, all of which can provide a result in less than an hour. We found that the rapid PCR test (the Cobas Liat) was just as sensitive at detecting the virus as our standard PCR tests. The rapid isothermal NAATs and the RATs were less sensitive than our standard PCR tests, limiting their utility.

Key Points

The Cobas Liat, a RT-PCR point-of-care platform that delivers a result in 20 minutes, performed equivalently to our standard RT-PCR; the major limitation of this platform is that only one sample can be tested at a time, considerably limiting throughput.
The rapid antigen tests and rapid isothermal NAAT assays demonstrated reduced sensitivity compared with standard RT-PCR, limiting their utility in a low prevalence setting.
Rapid antigen tests and rapid isothermal NAAT assays may be useful in the event of a widespread outbreak in New Zealand where laboratories are overwhelmed and unable to provide prompt results with existing resources. However, even in this setting their results would need to be confirmed with RT-PCR testing.
With time, changes in public health strategy and disease prevalence may widen the utility of these tests.

Journal/
conference: New Zealand Medical Journal

Organisation/s: ESR (Institute of Environmental Science and Research Ltd), Auckland City Hospital; Labtests; Southern Community Laboratories;

Funder: Competing interests: Dr Harte reports non-financial support from Abbott Rapid Diagnostics Pty Ltd, Siemens Australia and Rapid Test & Track, Sydney (supply of RAT devices for the trial evaluation). Acknowledgments: The manufacturers for supplying the rapid antigen test kits and rapid NAAT assays at no cost for our evaluation.

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