Virus testing accuracy questioned

The amount of confirmed COVID-19 cases worldwide has sprinted past the one million mark, but the actual number of infected is likely much higher due to people not being tested, and the tests that are administered are not always accurate.

The nasal swab for COVID-19, an invasive test that goes deep into the nostril, is one of the best we currently have, but that doesn't mean it's detecting all cases.

In fact it might miss as many as 30 per cent of them by returning false negatives, according to new research out of China.

Victoria's chief health officer Brett Sutton has recommended people who have symptoms of COVID-19 stay home even if they haven't been confirmed to have the disease.

"Certainly if people have a negative test it's the right thing to be at home and be away from others until you recover and you feel perfectly well before you get out," he said on Today on Friday morning.


It comes after Prime Minister Scott Morrison announced on Thursday that Australia has now tested more than 260,000 people, putting us in a world-leading position in terms of percentage of population tested.

"We are the first country, to the best of our knowledge, that has been able to exceed that mark," Mr Morrison said on Thursday.

More than 5000 of those tests have returned positive results.

The Government said most of the confirmed cases were acquired overseas, the vast majority of them in Europe, the Americas, or on cruise ships.

States and territories have also been publishing flight details where confirmed cases were on board with the hope of tracing the virus as it spreads.

"The testing resources that we are putting in place have been absolutely fundamental to our tracing … to ensure that we can restrain the growth and the spread of the virus," Dr Sutton said.

Where Australia's coronavirus cases have come from.
Where Australia's coronavirus cases have come from.


More tests are being developed that will hopefully be more accurate at detecting the virus in people who are only showing mild symptoms, if they display any at all.

"If we can get a rapid point of care test or bedside test, all the better. We need to be sure that's going to be a reliable test and one that's got the quality assurance that we need if we're going to roll it out," Dr Sutton said.

Yale medicine professor Harlan Krumholz warned even more accurate testing might not show the full scope of the virus' spread.

"Even with more testing, we are likely to be underestimating the spread of the virus," Dr Krumholz wrote in the New York Times.

"For now, we should assume that anyone could be carrying the virus. If you have had likely exposures and symptoms suggest COVID-19 infection, you probably have it - even if your test is negative."

He recommended people continue doing the things a lot of us already are - washing our hands religiously, not touching our face, staying in our homes as much as possible and avoiding getting too close to anyone who doesn't also live there.

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