Saturday, December 4

Covid-19: Middlemore Hospital on Rapid Antigen Testing Test

One of the first medical experts to test the latest Covid-19 Toolkit test explains how rapid antigen tests are used and if they are accurate.

Middlemore ED Hospital.

Middlemore Hospital Emergency Department.
Photo: Stephen Forbes / Stuff / LDR

Rapid antigen testing will play an important role in the future fight against Covid-19, and it is critical that the country is prepared.

That’s the opinion of a technical advisory group on testing for the virus, which released its report yesterday.

Middlemore Hospital in South Auckland was the first to test rapid antigen tests, or RATs, and its medical director, Pete Watson, said Morning report how tests are used.

“We were the first people to try this and we have been learning as we go about how to use it … what happens is that a person would have a nasal swab, the swab does not have to go as far back as the PCR test, so which is much more comfortable.It is placed in the front of the nose, twisted a couple of times and then it is taken out and placed in a tube where it is shaken with a little reagent and then poured into the kit.

“The test stays there for 10-15 minutes and then the result comes out, which is a couple of lines and depending on what those lines show, is whether it is a positive test or not,” Watson said.

“For us, the test has been about learning how to do it … making sure we are doing it correctly, there may be other tests that are simpler and more direct.”

The small test kits are similar in appearance to a pregnancy test, he said.

There are alternative saliva RAT tests on the market, but the Middlemore Hospital trial had only used the variety of nasal swabs, Watson said.

Due to questions about the sensitivity of the new tests, the hospital was using RAT tests in conjunction with standard PCR tests.

“At the moment, this is a test that we are doing in conjunction with the PCR test because again we are not sure of the sensitivity, so at the same time we are doing the standard PCR tests and sending them to the lab.”

Watson said some discrepancies were found between the results returned by the new RAT tests and the ‘gold standard’ PCR tests during the test.

“We are pleased that when we obtained a positive result, the PCR test was positive, that has been our experience, so we have ruled in those tests in which the RAT test was positive.

“But we’ve also had the opposite, where the RAT test came back negative, but we suspect the person had Covid, the CRP came back positive, and of course that’s the concern, the lower sensitivity of the RAT tests.”

Watson said the disparity in results demonstrates why health authorities are taking a cautious approach to implementing new testing methods.

“It is not a substitute for the PCR test and when you get a negative test, especially in someone who is symptomatic, it is very important that we continue to do so.”

“We’re looking here in the hospital setting in the emergency department, but clearly when these tests are rolled out for workers, workplaces and other settings, it will be around the frequency of testing that will make a difference.”

While the addition of RAT has provided some hope for Middlemore Hospital staff, Watson said the key step in protecting patients and staff is increasing vaccination rates among hospitalized patients.

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