Covid-19 tests that give result in 20 mins as good as traditional lab tests, study finds

Tests that can detect Covid-19 in just 20 minutes are as effective as the standard nasal swab testing done in laboratories across New Zealand, a study has confirmed.

PCR testing is considered the “gold standard” for determining whether a sample of saliva or nasopharyngeal secretions contains genetic material from the virus.

Usually, the process, which involves heating and cooling the sample and mixing it with enzymes, takes hours, but technology developed partway through last year can generate results much more quickly.

It is hoped the expanded use of the faster tests – known as rapid PCR tests – to triage patients in emergency departments with upper respiratory symptoms will help prevent the transmission of the virus in hospitals. But scientists say a global shortage of the kits needed to conduct them will likely stop them being more widely used.

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“They’re a very precious resource. These are just so critical to keeping our hospitals as free from Covid as possible,” said Otago University associate professor of immunology and microbiology James Ussher​, who co-authored the research, published in the New Zealand Medical Journal on Friday.

A person undergoes a nasal swab for Covid-19 in Stratford, Taranaki.


A person undergoes a nasal swab for Covid-19 in Stratford, Taranaki.

The study also looked at the accuracy of rapid antigen testing.

It concluded this process, which identifies the presence of specific proteins, such as spike proteins, on the virus, could miss up to 44 per cent of Covid-19 cases, compared with traditional PCR tests.

The wait time of up to 48 hours or more for results to traditional PCR swabs has previously led to calls from National’s Covid-19 spokesman Chris Bishop​ for rapid testing to be used more widely.

Health authorities also came under fire in September when a man at Auckland’s Middlemore Hospital shared a room with three other patients in a surgical ward while he was infectious with Covid-19.

In the wake of the incident, Director-General of Health Dr Ashley Bloomfield​ said the hospital was looking into why the man was not isolated while staff were waiting on the result of a PCR swab.

A Taranaki resident gets tested for Covid-19 after confirmation of a case in the community this month.


A Taranaki resident gets tested for Covid-19 after confirmation of a case in the community this month.

The publication of the paper, a collaboration by researchers from the Institute of Environmental Science and Research (ESR), Auckland City Hospital, Labtests and Southern Community Laboratories, came after the Government announced plans to spend $1 billion to bolster the contact tracing and testing system.

Associate Health Minister Dr Ayesha Verrall​ said on Thursday while standard PCR tests would remain the main tool used to diagnose Covid-19, from next Wednesday rapid antigen tests would be rolled out across the health system, including in rest homes.

Businesses would be able to buy rapid antigen test kits from approved suppliers to test their staff and the general public could get these at pharmacies on December 15.

Results from rapid antigen tests would be confirmed with a follow up PCR test.

She added that the Government would increase laboratory capacity so they could process 60,000 per day by early 2021 and would make saliva-based PCR testing and rapid PCR testing more available soon. However, she could not confirm details under what circumstances these would be used.

Ussher said despite their shortfalls, rapid antigen tests had a place in the Covid-19 testing system.

For example, they could be used to screen people crossing the Auckland border. Currently, this task was “taking up huge lab volumes and not turning up a huge number of positives”.

A nasopharyngeal swab is packaged before it’s sent for PCR testing.


A nasopharyngeal swab is packaged before it’s sent for PCR testing.

Dr Anja Werno​, a clinical microbiologist and virologist who heads up pathology for Canterbury Health Laboratories, agreed.

“Whatever is able to take pressure off laboratories and give a fast turn around time can be very useful in specific circumstances, such as critical [situations] in the emergency department for example …You’ve got an arsenal of test options that you can deploy and rapid PCR testing is one of them,” she said.

Darryl Carpenter​, who oversees Covid-19 testing and supply for the ministry, said it was considering rapid PCR test and monitoring research into them.

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