Allow me to explain the impact of a false positive rate of 0.8% on Pillar 2. We return to our 10,000 people who’ve volunteered to get tested, and the expected ten with virus (0.1% prevalence or 1:1000) have been identified by the PCR test. But now we’ve to calculate how many false positives are to accompanying them. The shocking answer is 80. 80 is 0.8% of 10,000. That’s how many false positives you’d get every time you were to use a Pillar 2 test on a group of that size.
The effect of this is, in this example, where 10,000 people have been tested in Pillar 2, could be summarised in a headline like this: “90 new cases were identified today” (10 real positive cases and 80 false positives). But we know this is wildly incorrect. Unknown to the poor technician, there were in this example, only 10 real cases. 80 did not even have a piece of viral RNA in their sample. They are really false positives.
I’m going to explain how bad this is another way, back to diagnostics. If you’d submitted to a test and it was positive, you’d expect the doctor to tell you that you had a disease, whatever it was testing for. Usually, though, they’ll answer a slightly different question: “If the patient is positive in this test, what is the probability they have the disease?” Typically, for a good diagnostic test, the doctor will be able to say something like 95% and you and they can live with that. You might take a different, confirmatory test, if the result was very serious, like cancer. But in our Pillar 2 example, what is the probability a person testing positive in Pillar 2 actually has COVID-19? The awful answer is 11% (10 divided by 80 + 10). The test exaggerates the number of covid-19 cases by almost ten-fold (90 divided by 10). Scared yet? That daily picture they show you, with the ‘cases’ climbing up on the right-hand side? Its horribly exaggerated. Its not a mistake, as I shall show.
Earlier in the summer, the ONS showed the virus prevalence was a little lower, 1 in 2000 or 0.05%. That doesn’t sound much of a difference, but it is. Now the Pillar 2 test will find half as many real cases from our notional 10,000 volunteers, so 5 real cases. But the flaw in the test means it will still find 80 false positives (0.8% of 10,000). So its even worse. The headline would be “85 new cases identified today”. But now the probability a person testing positive has the virus is an absurdly low 6% (5 divided by 80 + 5). Earlier in the summer, this same test exaggerated the number of COVID-19 cases by 17-fold (85 divided by 5). Its so easy to generate an apparently large epidemic this way. Just ignore the problem of false positives. Pretend its zero. But it is never zero.
This test is fatally flawed and MUST immediately be withdrawn and never used again in this setting unless shown to be fixed. The examples I gave are very close to what is actually happening every day as you read this.
I’m bound to ask, did Mr Hancock know of this fatal flaw? Did he know of the effect it would inevitably have, and is still having, not only on the reported case load, but the nation’s state of anxiety. I’d love to believe it is all an innocent mistake. If it was, though, he’d have to resign over sheer incompetence. But is it? We know that internal scientists wrote to SAGE, in terms, and, surely, this short but shocking warning document would have been drawn to the Health Secretary’s attention? If that was the only bit of evidence, you might be inclined to give him the benefit of the doubt. But the evidence grows more damning.