Perhaps unsurprisingly for a blog called "lockdown skeptics", this piece makes basic mathematical and epidemiological mistakes. In fact, very few positive COVID-19 tests are falsehttps://twitter.com/JuliaHB1/status/1307586325663698945 …
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The basic error presented here is the assumption that all PCR tests are run on a random population sample of the UK, for which the prevalence is 1/1000 This is inaccuratepic.twitter.com/5otBWj16Gn
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Most PCR tests in the UK (and everywhere) are run on the SUSPICION of COVID-19 In other words, it's a SELECTED POPULATION with a HIGHER PREVALENCE
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We can see this in the % positive of COVID-19 tests run in the UK. While it's relatively low now, it is still above 1% (i.e. >1/100 tests run come back positive)pic.twitter.com/nozHjsCgaE
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In other words, we EXPECT the rate of true positives to be FAR HIGHER in those receiving PCR tests than in the general population BY DESIGN So the central premise of the article is completely flawed
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I'd say it's not unlikely that there are 10-20% false positives, depending on the population sampled, but since many/most people who get a positive PCR test are re-tested it's largely a non-issue in terms of the statistics
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Replying to @philochsghost
To be fair, that's coming from the context of NSW where the % positive is currently sitting at 0.07%. Even if lab contamination only happens in 1 test per 10,000, we'd have as many false positives as real ones here!
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That being said, virtually every positive is retested, so the *true* rate of false positives in the record is probably 0% or close to that
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