What is a false positive coronavirus test? How is it possible?

coronavirus test : There is relief and anger in the central queensland town of blackwater after the revelation the youngest australian to thought to have died of covid-19,

What is a false positive coronavirus test? How is it possible?

Nathan turner, may not have been infected with the virus.The news has only compounded the grief for his widowed fiancé simone devon, who has had to deal with her loss in isolation.

The community is outraged by the test confusion, but is it fair to blame queensland health authorities?

The situation is complicated by the fact mr turner had underlying health conditions and flu-like symptoms.

While the mining town has received an apology from the queensland premier, locals are demanding answers.

What is a false positive?

In the case of covid-19 test kits used in australia, virus expert associate professor ian mackay from the university of queensland said the kits were very robust, sensitive, reliable and quite precise.

But he also said no test was perfect.

Dr mackay said the virus moved around the body, so where the sample was taken from could be critical.

If the virus was lurking in a person’s lungs at the time of testing, but the swab was taken at the back of the nose it may not be accurate.

“it is more likely that there was actual virus in that particular person at some point, and it was a late positive, which means most likely it would be the end of an infection, if anything,” dr mackay said.

But a false positive could also come from human error.

“usually due to a lab being contaminated with the virus or with product from a previous test,” associate professor mackay said.

What is a false negative?

A false negative is when the person being tested for coronavirus has symptoms and is positive, but tests negative.

The abc’s dr norman swan said there had been incredibly “high” false negative rates worldwide.

One of the reasons dr swan points to is that the testing kits have been fast-tracked as the pandemic hit.

“the genetic test came into practice in january without the normal evaluations and checks and balances that would happen with a pathology test just to get it into service,” dr swan said.

“it is only now that the accuracy is becoming clear.”

He said the results depended on where the patient was in the infection cycle.

“right at the beginning, if you have just had the infection and just happened to get tested, it is almost always negative because there is just not enough virus around,” he said.

“but even when the symptoms break out, it can be 60 per cent of people who are negative, are actually positive.

“and then three days fter the symptoms break out, it goes down to about 20 per cent and then it goes up again.”

Dr swan said, “overall, on average, the majority of people who get the coronavirus test, it is accurate, but there is a significant minority where it is negative”.

“i think the message here is it is not that it is a lousy coronavirus test, you just need to know its limitations,” dr swan said.

“if you think you have covid-19, loss of taste, loss of smell, funny symptoms, and your test comes negative — have the coronavirus test again because it could well be positive.”

Dr swan cited a report by the johns hopkins university in the usa that found the chance of coronavirus test giving a false negative reading were greater than one in five.

Dr swan told abc breakfast the study was a vital one, because it looked at seven different studies into false negatives.

How many coronavirus test did nathan turner have?

The 30-year-old man from blackwater had two initial tests, then multiple follow-up tests days later.

Queensland chief health officer jeannette young said the first test had come back positive for covid-19.

“on the night i was told that the gentleman was positive, i immediately asked for a second to be done and it was urgently sent to rockhampton,” she said.

“he had been dead for several hours at that point.”

The secondcoronavirus test came back negative.

“it was ruled as invalid because the coronavirus testwas contaminated with blood,” dr young said.

She said she then asked — through the coroner’s office — for the body to be urgently sent to brisbane for a post-mortem.

That post-mortem found no sign of the virus.

“[the] coronavirus testcould be negative because the virus had denatured during that time,” dr young said.

Multiple subsequent coronavirus test have all been negative.

Dr young said nothing could have been done any differently.

So, did he have the virus or not?

There are two potential answers here.

Dr young said, “one is that it was a false positive, the other is that it was a true positive — and we won’t know which it was”.

Associate professor mackay said the autopsy report found mr turner had not died of covid-19.

“certainly at the moment there was no active infection present, but what may have happened is that it was the end of a previous infection — the coronavirus testmay have detected a little bit of that going on,” he said.

But no-one knows.

The coroner is continuing to look for mr turner’s cause of death, and is doing more coronavirus teston his body.

This news was originally posted on abc.net.au

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