This explains false positives https://www.google.com/amp/s/www.bbc...s/amp/54270373Quote:
Originally Posted by Mark G
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This explains false positives https://www.google.com/amp/s/www.bbc...s/amp/54270373Quote:
Originally Posted by Mark G
Hi Mark - we have covered this extensively on the forum so at risk of repeating myself to some of the avid followers of the thread here goes.Quote:
Originally Posted by Mark G
If I get a bit of terminology incorrect I apologise, but I firmly believe the thrust of what I am posting here is correct.
All tests have a False Negative and False Positive rate and they are usually declared. They refer to the clinical, laboratory errors that are associated with all tests.
Normally these FNs and FPs are declared so that analyse can take the range of error in to account.
With the PCR test, these figures have not been declared.
In addition to the technical shortcomings of tests, there can be additional shortcomings and this is particularly relevant where Guinea Pigs are mostly using home testing kits, or turning up at outdoor testing stations where mostly non-clinically trained staff are handling the testing process and batches of samples are being picked up at times by self-employed couriers and taxis, more often handling Just Eat deliveries or Hermes orders from Next.
As Governments haven't declared the FNs and FPs for the PCT tests, there has been analysis of various findings that have led to a consensus on FNs in the range of 20-30% and of FPs in the range of 0.8% to 4%.
I'm going to set out some illustrations now using 20% and 0.8% to give you an idea of outcome.
Scenario 1.
In hospital testing where likelyhood of CV infection is high and assuming a 50% rate of infection with CV.
Test 1000 people. Expect 500 positives.
400 Positives will test positive.
4 Negatives will test positive.
596 test negative.
The consequences are that 400 will be treated correctly, 4 people might be treated incorrectly as having CV but they clearly have a severe respiratory illness as they are in hospital.
96 people will not be treated as having covid who should, but repeat testing will end up catching most.
Most importantly, the testing results whether right or wrong are backed up by a clinical diagnosis.
Scenario 2.
General Public Testing where most are not showing any symptoms and community infection is thought to be 1%
Test 1000 people. Expect 10 positives.
8 positives will test positive.
8 negatives will test positive.
984 will test negative.
The consequences are that 2 of the infected cases will go about their business as usual. 8 will be quarantined, kept off work without genuine cause.
The figures are inflated by 60%. Policy decisions are based figures that are out by a significant amount.
Scenario 3.
Covid has disappeared from the general population.
Test 1000 people. Expect 0 positives.
There are no positives to test negative as a result of the FN error.
8 negatives will test positive.
The consequences are that Covid can not be eliminated. That this rate of FPs gives us a community rate of 800 per 100,000 population.
Here is the table for the Top 30 Middle Layer Super Output areas (statistical areas of around 7500 population).
https://twitter.com/RP131/status/133...407747/photo/1
Our Scenario 3 would fall in to 4th place at the moment nationally, be placed in Tier 3 and yet the reality is that there is no community infection.
I hope that sets out in a straightforward way the problems that have been highlighted around use of the PCR test for mass public surveys. It's an issue that I first came across in July, but experts at Porton Down flagged it up to SAGE in May, asking for SAGE to deal with this.
The problem with this explanation is that it asserts that the people attending the test centres were symptomatic.Quote:
Originally Posted by Fellbeast
1. Symptomatic of what? September is rhino virus season. Back from holidays, back to school, back to University and so it cannot be assumed that even someone with symptoms had Covid.
2. Mass testing was taking place in schools and Universities - no symptoms required.
3. Local authorities often had a "Come of Down" policy for their mobile testing centres, such as here in Blackburn where as late as 9th September the Council announced on Facebook that anyone can be tested.
They even had teams going around knocking on doors asking people to sign up for a test.
4. People were booking tests and ticking the appropriate symptoms box to get a test. Sometimes prior to, or after travelling overseas.
So whilst it sets out the issue of false positives, it seeks to discredit the validity of the concerns raised.
BBC speaks with forked tongue.
The test’s instructions for use state that it should not be used on asymptomatic people.
https://www.bmj.com/content/371/bmj.m4436
WP, do you believe epidemiologists are not taking false positives into account when analysing results from mass testing?
As WP points out, the nuances of false negative and false positive categories can take a while to get your head around.
Add to that the fact that the principles of epidemiology and disease control can also be nuanced and poorly understood by the general population and then stir in a healthy dose of fake news/conspiracy theory and you can appreciate that this whole sh!t-show is almost impossible to navigate through. Especially for a politician who is unlikely to be trained in any of the above and also subjected to all the other distractions such as the economy, keeping voters happy etc etc.
The main news channels like to give nice, easily digestible packages to the great unwashed but the daily stats they show are pretty meaningless. Would be much better to give daily capacity figures for NHS regions. If you knew that your local hospital was full (as in Stoke on Trent) then you might think twice about doing anything risky or ignoring covid advice.
As a number of people on this thread like statistics here are a few figures to consider:-
Member and number of posts on this thread.
Witton Park 548
Dave_Mole 326
Oracle 262
Mike T 251
Fellbeast 238
Stagger 231
Muddy Retriever 229
Graham Breeze 226
Travs 144
Llani Boy 117
Flem 108
Mossdog 87
molehill 83
Wheeze 81
anthonykay 63
noel 61
JohnK 61
Derby Tup 51
Wetherby whaler 40
CL 33
Mark G 24
bigfella 22
Daletownrunner 21
MattPo 19
Steph 18
jackd 17
RichA 16
Marco 15
TheGrump 15
PeteS 14
mr brightside 12
creaky 11
brett 10
There may be a few false positives or non-negatives in the above figures:p
I can't answer that. Epidemiologists are not a group that has one opinion on this.Quote:
Originally Posted by noel
But consider the makeup of SAGE.
No Clinical Immunologists.
No Biology Degree.
There are a few medics, some sociologists, psychologists.
They do have 7 mathematicians - the discipline most represented.
People think SAGE is a co-opted group of people that are experts in virology/immunology. I thought as much. BUt they aren't and that was clear when the membership was published.
https://www.bmj.com/content/bmj/369/bmj.m1808.full.pdf
This was May.
It is highlighting the lack of the "Gold Standard" for the Covid test. At that time they are looking at it from the perspective of a False Negative because the prevalence in the particular setting is high.
More recently the concerns have moved to the False Positive, because the test has been used among the public en mass, and the prevalence there is low.
Being generous, I think the issue is one of mindset. Ferguson et al have over egged the potential of outbreaks in the past.
What are the consequences of being wrong on the side of caution?
Imagine if Ferguson had modelled 25k would have died of Covid without a lockdown? Better to be on the high side.
Being ungenerous, I sense a political motive behind it.
Academia and the Public Sector are steeped in the left.
In the UK they abhor Brexit and the Tory Government, as exemplified by the Dr Deepti Gurdasani quoted by Mike.
Across Europe they have Le Penn, AFD, Salvini....
In the USA Trump.
The western world was heading the wrong way. What better way to enact a handbrake turn?
and it should require two positive tests and a diagnosis to confirm a case. It would make it much easier for all.Quote:
Originally Posted by Wheeze
already out of date ;) but I have to say Oracle is impressive in 3rd place as he was only contributing for around 1/3 of the time the thread has been running.Quote:
Originally Posted by XRunner
In mitigation for myself and like-minded people, we have been a little out-numbered (2 have been banned) so tend to post more than others to answer questions or deal with points raised, a roleI currently seem to share with Muddy.
MR - you need to pull your weight a little more and lighten my load :D
Posting to keep ahead of Wheeze and try to catch Mossdog on the leaderboard.
Not sure I even trust the leaderboard statistics, they could be fake stats.
I think it would be a shame if this thread turned into another master maker. We should all do our best to keep our posts to the point and not stray off subject.
As I am not an Epidemiologist, Mathematician, Virologist, Immunologist, Psychologist, Sociologist, Economist or even a Politician how on earth have I managed 117 posts and 10th place on the list:confused:Quote:
Originally Posted by XRunner
I must have posted some rite shite:eek:
You certainly won't see me trying to climb up the leader board by posting needlessly in a thinly veiled attempt to get level with anthonykay.
I think Xrunner needs to do the count properly, counting words or maybe square yards of words not posts. The oracle would be ahead closely followed by WP, with the rest of us miles behind :)
I will excuse my embarrassingly high total of 144 (now 145) by saying that at least most of my posts have been moaning about not being able to race!!!
Make the most of being ahead moley!😂😂
You’re doing such a good job without my help though. 😃 Anyway only one more needed to draw level with Stagger.Quote:
Originally Posted by Witton Park
Obviously I'm not going to take the bait. Although I can't understand how I managed to make 63 posts, given that for the last few months I have found this thread too boring to pay much attention to it.Quote:
Originally Posted by noel
Got a text message from my GP surgery today to say that they have now got flu vaccinations available for the 50 - 64 age group.Quote:
Originally Posted by Llani Boy
Booked in for 12.43 on Sat 5th Dec:)
"Would I encourage someone to hug and kiss their elderly relatives? No I would not...If you want them to survive to be hugged again." Chris Whitty, Chief Medical Officer for England.Quote:
Originally Posted by Witton Park
"would you encourage someone to hug and kiss an elderly relative who was dying? Well good luck with that, because they'll probably not get within 10 yards of them."Quote:
Originally Posted by Mike T
Richard Taylor - Chief FRA Forum Covidiot
Thanks for your reply re false positives WP.
Indeed. The assumptions/calculation approach used for WP’s scenarios aligns with the logic presented in the BBC article, so the experts the BBC consult with must know what they’re talking about after all...
as I've said, the problem with the BBC article then goes on to present a scenario that isn't what was happening out there in the real world.Quote:
Originally Posted by nearlyhopeless
If you recall, mid September the Govt had a problem with the testing system breaking down. People were just being tested, no symptoms, apparently over-loading the system.
We know they were mass testing schools and universities.
So the premise that false positives is an issue, but actually it isn't because only people likely to have covid are being tested, is where the BBC have strayed beyond where they reasonably should, suggesting they have a narrative.
They have been testing up to 395,000 a day - you think 395k a day have COVID symptoms?
https://coronavirus.data.gov.uk/details/testing
Here is the graph showing the number of PCR tests done.
Does that look in line with symptoms in the public?
Good question. I've no frame of reference here. Clearly this many people don't have covid. Although, I suspect a lot of people have respiratory symptoms at this time of year with various colds/flu so might be worried they do have it. Do we have any data on how many people are being routinely tested (ie, without symptoms)?Quote:
Originally Posted by Witton Park
Further to our ongoing discussion about the effects of false positives (and negatives), it's important to know whether people who are being tested have symptoms or not, since that affects how you interpret the data.
From personal experience, people in the ONS screening study (like me) are included in these figures. And I've been tested about 6 times now without having any covid symptoms.
https://www.blackburnbid.co.uk/covidtesting/
Scroll down to "About the mobile testing unit"
"Anyone can be tested – you don’t need to have symptoms of coronavirus."
14th July.
This was going on through to mid September. It was certainly happening in the areas that were in special measures which was most of the North and large chunks of the Midlands.
In mid September when they started hitting the Universities, they ran out of tests and all of a sudden started to back pedal and ask for only those with symptoms.
In Blackburn I think that was 14th September. There was on day where the posted a Come on Down, everyone welcome and by the end of the day they had a "only with symptoms".
By switching to students, the testing of asymptomatic has been extended at the very least from July to October and should be cause for concern.
From Chris Giles, FT, with the last sentence from Owen Jones, The Guardian:
"A cautious estimate of the number of excess UK deaths linked to coronavirus since mid march has passed a new marker and stands at 80,100 Of these 75,200 have happened and the rest are estimates bringing lagged official data up to date When measured properly, it is clear that the second wave has been far less deadly than the first. My estimates suggest that excess deaths are now beginning to decline.
Why should you believe these numbers? a) Because the updating model is proving remarkably accurate in the second wave (I'm surprised how accurate) b) This welcome feature stems from better Covid testing, so daily hospital deaths pick up roughly all excess deaths this time.
FWIW - an extremely speculative estimate of the R number based on my excess deaths series suggests it was hovering around 1 just before lockdown and persistently went below 1 after Nov 2nd start of lockdown.
"That means around 1 in every 832 Britons have so far died in the coronavirus pandemic, a hideous death toll made possible by a government which locked down too late and re-opened the economy without a functioning Test and Trace system."
In normal times, 1 in 132 Britons die every year....a hideous death toll made possible by Life, a sexually transmitted, universally fatal disease!
And yeah every year everyone tries there hardest to stop people dying, help cure them or advise them on best practice to reduce the chance of dying. Think of all the effort and research that goes into and has gone into cancer research. And every other illness and ailment. Are you suggesting we just don’t bother with covid?Quote:
Originally Posted by Wheeze
Presumably 80,000 dead (so far) is acceptable? You know compared to just over 900 deaths in Australia and just over 500 in South Korea?
Well i've had to gracefully drop out of the Skirrid Fell Race later this month... a combination of us being in Tier 3, and the current ban on going into Wales, not to mention their impending increased restrictions, i messaged the RO and asked him to offer my place to a local.
Although have entered the 50th Welsh 1000metres, which hopefully will go ahead as a normal race next summer!
Are you OK? I used to find your posts interesting and coherent even if I disagreed with them. Now I'm struggling.Quote:
Originally Posted by Mike T
Just back from a 3 hour walk on the hills. Very nice.Quote:
Originally Posted by noel
Just a further mathematical issue with the data.
Note that our areas are being judged on positive tests per 100,000.
Made up figures here, but let's say Blackburn were turning up 6 positives from 1000 tests end August and early September, that equates to a local rate per 100,000 population of 600.
Then the Govt issue their dictat that only symptomatic. The Local Authority echo that.
They still get the 6 positives, only 800 test though as 200 of the asymptomatic drop off.
Then they have a rate of 750 per 100k.
A 25% increase - yet there are no more cases, they've just cut out some of the asymptomatic guinea pigs.
That's an increase regardless of any issues with testing inaccuracies.
That's a surprising figure - I would have expected it to be 1/average life expectancy, say 1 in 80 or so.Quote:
Originally Posted by Wheeze
Although people die at younger ages for all sorts of reasons that figure is surely reflected in life expectancy so 1 in 132 seems quite good odds in the face of it.
I think I'm OK! I find Chris and Owen interesting people to follow, and thought others might find them interesting too. The UK figures are so bad - per capita, the UK has seen more deaths from Covid than the USA has at every point in the pandemic - and yet lots barely raise an eyebrow, including the newsreaders on the BBC. It is good to see intelligent people taking the figures seriously.Quote:
Originally Posted by Witton Park
Perhaps the UK figures are so bad because, prior to Covid, the NHS has been extraordinarily excellent in extending life for very old, very vulnerable people with lots of comorbidities, much more so than somewhere like the USA with it’s less loving health system. Then something new hits, and gets into care homes, and, oh dear. It’s why African countries have such low death rates, their average age is 15 or something. We don’t all start from the same place.
But remember, prior to Covid, the average 80 year old, with the average number of medical problems that an 80 year old has, would live for another 9 years if a man, and 10 years if a woman. I don't think we can attribute the high number of deaths in the UK to the NHS having left low hanging fruit - the pandemic has just been badly managed in the UK full stop.Quote:
Originally Posted by Wetherby whaler
Quote:
Originally Posted by Wheeze
The simple method of calculating the above figure would be to take the total UK population of 66m and divide it by the number of deaths per year of 660,000 i.e. 1 in 100!Quote:
Originally Posted by Mark G
How the UK population is counted and how deaths are counted will significantly change the figure.
e.g. the population and number of deaths may include tourists and migrants - both immigrants and emigrants.
and they still areQuote:
Originally Posted by Mike T
Really sad news - coronavirus has claimed Pete Bland 😔. There’s an announcement on Facebook