Mass testing in schools as children returned this week is resulting in hundreds of positives – but viral prevalence is now so low that the large majority of them are wrong and result in children and their contacts isolating needlessly. Sarah Knapton in the Telegraph explains.
Biostaticians are concerned that infections in the community are now so low, that false positives and negatives are vastly outnumbering true cases, leading to real cases being missed and families needlessly being asked to isolate.
Pupils are currently being tested twice a week for coronavirus using lateral flow devices, but real-world data has shown they miss positive cases around 50% of the time.
Similarly, although they pick up 99.9% of negative cases, meaning fewer than 0.1% will be false positives, the prevalence rate is now low enough that false positives will be making a significant contribution to the overall figure.
Previously, positive tests were confirmed using a more accurate polymerase chain reaction (PCR) lab test, but this week the Government admitted it had quietly scrapped the process at the end of January.
It means that thousands of pupils and their families are having to isolate needlessly, and missing more school after months away from classrooms.
The latest figures from NHS Test and Trace in secondary schools found 328 positives out of 663,332 tests between February 25th and March 5th. That’s 1 in 2,000 pupils, which is far lower than the 1 in 270 that the latest ONS survey suggests is the current community prevalence. Some are concerned this means large numbers of cases are being missed, though the PCR-based ONS survey picks up many of the non-infectious cold positives which the less sensitive lateral flow tests (LFTs) do not. There is no reason to regard missing cold positives as a problem, particularly given the personal and economic cost of isolating positive cases.
In primary schools, 613 positives were found from 721,546 tests, or about 85 in 100,000. This gives an overall school prevalence rate of about 0.067%.
At this rate (if it were the true prevalence), out of a million tests 670 should come back as true positives. However, with a 0.1% false positive rate (a conservative estimate for LFTs, which were found in a report to have a 0.32% false positive rate) there would also be 1,000 false positives. That means 1,000 out of 1,670 positives, or around 60%, would be false. Of course, the 670 positives per million from the last couple of weeks of testing include the false positives, so the actual proportion of false positives will be higher.
Professor Jon Deeks, a biostatistician from the University of Birmingham, told the Telegraph:
We would expect far more false positives than true positives amongst those testing positives in schools. There are many uncertainties but given the DHSC data it seems likely that over 70% of positive test results are false positives, potentially many more. Addition of a confirmatory PCR would add little cost and would most likely reduce false positives to 1 in 1,000,000. The refusal to confirm lateral flow results with PCR is at best perplexing, will make testing less attractive, and create harm by wrongly isolating individuals, families and other close contacts.
Confirmatory PCR testing for LFT positives is unlikely to help, however, in terms of weeding out cold positives, as the PCR tests are much more sensitive than the LFTs (picking up many more cold positives) and so are unlikely to give a negative where an LFT has come out as a cold positive.
There is also the question of how many of the tests have been incorrectly carried out, perhaps on purpose, if self-administered, to avoid having to isolate?
Mass testing in schools was always a bad idea – cruel, intrusive, pointless. The high proportion of false positives, with their needless and disruptive requirement to self-isolate, only underlines that fact.
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As a non-subscriber,I was able to read the beginning of the Times piece by Dear Ickle Grovelling Janice, who, when asked by some shop dork to put on face knickers, immediately complies with gabbled apologies.
Janice, you are what is wrong with this country. Go bury yourself, still in your filthy knickers.
Hi Annie, is that really you ?
Just finished your piece, yes I think it is, welcome back.
Never been away, but principal place of residence is now Reddit.
From the roundup.
Vaccine permit to visit the pub ?
As a young and middle aged man I spent part of most evenings in the pub, not to get pissed but to socialise and keep in contact with friends (and meet new ones!) before the internet.
During lockdown Lite, ie last summer + going into Tiers, I went out of my way to patronise local pubs and licenced eateries especially those that kept Track’n’Trace to a minimum.
I can now live without pubs and nightclubs so stuff their ‘permit’ though I will attempt entry now and then just to prove my point.
Todays youngsters were already having less sex and visiting pubs less often as a result of growing up on t’interweb, lockdown has reinforced this.
Bye Bye wet pubs but that always was the aim of Alcohol Concern and the like.
The Big Reset. Close all pubs, stop holidaying abroad, stay home and don’t socialise. Only those considered important will be allowed to do what we used to take for granted.
Meanwhile the offspring of rest will be left wondering why their oldies used to actually enjoy travelling abroad and going to the pub ‘to do what exactly’ ?
From the roundup
‘Health Security body gives UK Protective Shield’.
It’s from Hancock so obviously bollocks. I don’t require yet more life unenhancing interventions in the name of Public Health (ie medico facism).
A mishmash of PHE, Track’n’Trace, the JBC and various failed individuals. I suspect its real aim is to wrest (?) control of Public Health policy from the provinces back to Whitehall.
Good luck with fight but let’s get the popcorn out.
I can’t wait until the circular firing squad/blame game/throwing each under under buses. Govt, PHE, SAGE, media. Who lied to who? Who gets the ultimate blame? There isn’t enough popcorn in the world. I expect Anders Tegnell to be investing heavily in corn share futures
sounds like nothing more than pricey “rebranding” to me – same old same old but 4 under one umbrella. Rearranging the deckchairs on the titanic springs to mind.
A Titanic that goes actively looking for icebergs to hurl itself against.
Welcome aboard Ben.
After 12 months ‘opposition’ to the bozo, hancock van tam claque by demanding ‘Sooner, Harsher, Longer Lockdown’ veteran Labour MP for Exter Ben Bradshaw has announced that he will not be voting to renew the Coronovirus legislation because
‘Police State’.
They say a leopard cannot change its spots. Watch this space.
Pic h/t Radio Exe.
The “pubs” have bemoaned for years about the number that close, week in and week out.
If they insist on face nappies and vaccine “passports” then they must have a “mass” suicide wish.
A few weeks into the current lockdown the landlord of my unlovely local pub was reduced to selling tins of unused mixed vegetables and even what appeared to be soft coverings from the limited exterior smoking area.
Whether this was to assist the newly destitute or to raise a few quid to feed himself was not at all clear.
From the roundup
‘I’m Janice, get me out of here !’
Free yourself, stupid bitch. You appear to have benefitted from an enhanced education and from the way you describe your own behaviour you have no faith in lockdown regulations yet the moment you are challenged you kop out and cave in.
No-one is gonna save You Janice, you have to save yourself with your privileged resources.
Couldn’t agree more. Bumsucking little twat she is.
I hadn’t noticed your post about her first Annie.
Cameron Covid Conperson ?
Guardian has it all.
pub owner friend of mine has said after what the government have done to his industry, he spent a fortune ‘making it safe’ only to have it shut again, that anyone is welcome, he needs to make some money. Plus friends who dashed off to get their jab thinking it would get them a holiday this year are feeling angry. The backlash is still to come.
papers for the pub
https://www.bbc.co.uk/news/uk-politics-56517486#comments
sort by best rated comments and you will see the worm is finally turning
I will not be visiting any establishment that requires I show my ‘papers’ before being allowed in. As much as I enjoy going to my local pub I’ll continue drinking at home.
I’m struggling a bit today with asymptomatic long lockdown.
If we are to have vaccine passports are we also to have HIV test passports too?
If not why not?
If one is ethical, so is the other.
maybe ‘STD free’ tattoos
Health Security body gives UK Protective Shield – Launching on 1st April is all we need to know
Is it an April Fool?
Correct
Perennial fool probably.
For some reason my Reddit has ‘lost’ the Lockdown Sceptics group. Can anyone point me to it?
https://www.reddit.com/r/LockdownSceptics/