@UnHerd asked me to write about school testing – and why PCR matters so much.
From @DHSCgov data I estimate 70%-95% of school positive cases could be false. Hope I’m wrong, but unless PCR confirmation is done we will never know.
unherd.com/thepost/why-th…
1/8
From @DHSCgov data I estimate 70%-95% of school positive cases could be false. Hope I’m wrong, but unless PCR confirmation is done we will never know.
unherd.com/thepost/why-th…
1/8
The mistake being made is to think that all that matters is that false positives are rare. However, if true positives are even rarer then we are in trouble. Test positivity data from Test-and-Trace (1 in 1500 positive) raises serious concerns that is the case.
2/8
2/8
If 1 in 100 pupils had Covid-19, we would be fine. Five out of every six test positives would be true positives. But it looks like we are somewhere between 1 in 1,000 and 1 in 10,000 (we don’t know).
3/8
3/8
If 1 in 1000 had Covid-19, two out of every three positive tests would be false positives
4/8
4/8
If 1 in 10,000 had Covid-19, 19 out of every 20 tests would be false positives
5/8
5/8
Confirming with PCR would reduce the false positive rate down to 1 in a million. Completely solves the problem. And very few people need to get confirmed (about 0.15% at 1 in 1000 prevalence).
6/8
6/8
There will be a small drop in cases detected – recent data suggest sens of PCR for the infectious cases is 90%. At 1 in 1000 prevalence we would miss one case for every 20 FP released, at 1 in 10,000 it would be one for every 200 FP released
7/8
7/8
And remember every FP means a pupil or teacher, their family, their dog and their school bubble will be locked up wrongly for 10 days. 1 FP could mean 35 people.
It’s not an attractive proposal, and clearly will harm peoples' lives and our childrens' education.
8/8
It’s not an attractive proposal, and clearly will harm peoples' lives and our childrens' education.
8/8
@DHSCgovuk @educationgovuk @SMHopkins @JimBethell @MattHancock @GavinWilliamson @NickTriggle @deb_cohen @PHE_uk @SMC_London @CMO_England @ScienceShared
@DHSCgovuk @SMHopkins have just published this which does not address the argument. More than willing to talk as always to help - but hopefully the above is clear enough.
You have to make testing acceptable to parents - and this set-up isn't
gov.uk/government/pub…
You have to make testing acceptable to parents - and this set-up isn't
gov.uk/government/pub…
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