Data, Stats & Daily Numbers started 27th Feb

[boys3]

UK govt pressers Slides & data www.gov.uk/government/collections/slides-and-datasets-to-accompany-coronavirus-press-conferences#history
R estimates UK & English regions www.gov.uk/guidance/the-r-number-in-the-uk
Imperial UK weekly LAs, cases / 100k, table, map, hotspots statistics Attendance explore-education-statistics. service.gov.uk/find-statistics/attendance-in-education-and-early-years-settings-during-the-coronavirus-covid-19-outbreak
NHS England Hospital activity www.england.nhs.uk/statistics/statistical-work-areas/covid-19-hospital-activity/
NHs England Daily deaths www.england.nhs.uk/statistics/statistical-work-areas/covid-19-daily-deaths/
Cases Tracker England Local Government lginform.local.gov.uk/reports/view/lga-research/covid-19-case-tracker
ONS MSAO Map English deaths www.england.nhs.uk/statistics/statistical-work-areas/covid-19-daily-deaths/
CovidMessenger live update by council district in England www.covidmessenger.com/
Scot gov Daily data www.gov.scot/publications/coronavirus-covid-19-daily-data-for-scotland/
Scotland TravellingTabby LAs, care homes, hospitals, tests, t&t www.travellingtabby.com/scotland-coronavirus-tracker/
PH Wales LAs, tests, ONS deaths Dashboard app.powerbi.com/view?r=eyJrIjoiZGYxNjYzNmUtOTlmZS00ODAxLWE1YTEtMjA0NjZhMzlmN2JmIiwidCI6IjljOWEzMGRlLWQ4ZDctNGFhNC05NjAwLTRiZTc2MjVmZjZjNSIsImMiOjh9
ICNRC Intensive Care National Audit & Research reports www.icnarc.org/Our-Audit/Audits/Cmp/Reports
NHS t&t England & UK testing Weekly stats www.gov.uk/government/collections/nhs-test-and-trace-statistics-england-weekly-reports
PHE Surveillance reports & LA Local Watchlist Maps by LSOA www.gov.uk/government/collections/nhs-test-and-trace-statistics-england-weekly-reports
ONS England infection surveillance report each Friday www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/bulletins/coronaviruscovid19infectionsurveypilot/previousReleases
Datasets for ONS surveillance reports www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/datasets/coronaviruscovid19infectionsurveydata/2020
ONS Roundup deaths, infections & economic reports www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/articles/coronaviruscovid19roundup/2020-03-26
Zoe Uk data covid.joinzoe.com/data#interactive-map
ECDC rolling 14-day incidence EEA & UK read https_www.ecdc.europa.eu/?url=https%3A%2F%2Fwww.ecdc.europa.eu%2Fen%2Fcases-2019-ncov-eueea
Worldometer UK page www.worldometers.info/coronavirus/country/uk/
Our World in Data GB test positivity etc, DIY country graphs ourworldindata.org/coronavirus/country/united-kingdom?country=~GBR
FT DIY graphs compare deaths, cases, raw / million pop ig.ft.com/coronavirus-chart/?areas=gbr&areas=fra&areas=esp&areas=ita&areas=deu&areas=swe&areasRegional=usny&areasRegional=usnj&byDate=1&cumulative=1&logScale=1&per100K=1&values=deaths
Alama Personal COVID risk assessment alama.org.uk/covid-19-medical-risk-assessment/
Local Mobility Reports for countries www.google.com/covid19/mobility/
UK Highstreet Tracker for cities & large towns Footfall, spend index, workers, visitors, economic recovery www.centreforcities.org/data/high-streets-recovery-tracker/

⏭ Our STUDIES Corner ⏮www.mumsnet.com/Talk/coronavirus/3869571-Studies-corner?msgid=99913434

We welcome factual, data driven and analytical contributions
Please try to keep discussion focused on these

Can I ask, without sounding mardy, why there is more focus on false positives with LFTs than false negatives, which I believed to be FAR more common : and also far more of a problem?

@Piggywaspushed

Can I ask, without sounding mardy, why there is more focus on false positives with LFTs than false negatives, which I believed to be FAR more common : and also far more of a problem?

My view on why: 1) The results are so low that they are below the expected false positive line, this is a chance for science to learn something. 2) We can't do anything about false negatives unless you'd like to PCR test everyone? 3) Kids have missed a lot of school, the risk of a whole class being off due to a test error is a problem. 4) False negatives have had their impact wildly over-stated. The cause of most false negatives is the results aren't at a level high enough, that means they aren't infectious. Many may have recovered from covid already - no issue. Others may always have low viral load, too low to be infectious - again, no issue. Finally the problem cases, those who are just starting to become infectious, this is why they're tested twice per week. 5) The cases of those who don't do the test correctly but the test doesn't identify as inconclusive... They won't do a PCR test correctly either, unclear what you want done - blood tests? 6) Cases are dropping dramatically; the chances of infection are currently really low. When cases are high and rising I'll agree with you it's something to be concerned about. But cases are low, so there's a balance of potential harms.

OK, thanks : I just feel like the narrative has changed and the government my be rowing back towards not isolating close contacts.

I don't have high confidence that the students will do twice weekly testing at home in huge numbers to be honest. Obviously from a health and safety in the workplace pov , I am far more worried about false positives but I appreciate there shouldn't be that many at the moment. I also fear the the 'they have missed out on so much' narrative is driving behaviour and decision making a lot.

I know case numbers are dropping but I also do remember a time when we were jittery because they went over 1000!

I also wonder what happened with spit/saliva tests?

Spit tests are still coming through trials: www.bbc.co.uk/news/amp/health-55840547.

The situation changes @Piggywaspushed, and that changes the concerns. I think it sounds mistrustful on your part to keep referring to many of these topics as "narrative", rather than allowing that others might simply have a different view than you have on overall balance of harms.

But do you remember the furore cause by Julia Hartley Brewer back in the late autumn about false positives? Completely unscientific and was corrected by Spiegelhalter. That was all before rates were this low wasn't it?

When you say 'keep' I think I did it twice in post? I was referring to government and media narrative : which definitely exists. It is a term widely used by sociologists and behaviouralists... (eg we need to change the narrative around catch up was said last week by the BPS or 'there is a harmful narrative about masks/vaccines in some sectors')

I am mistrustful of the DfE definitely!

Thanks for info on spit tests.

I misremembered, it was early autumn and not specifically about PCR tests:

www.google.co.uk/amp/s/www.independent.co.uk/news/uk/home-news/coronavirus-false-positives-testing-covid-19-test-b550133.html%3famp

Sorry, meant not specifically about LF tests!

@Piggywaspushed @MRex

I had a similar feeling when I read the BBC article. It mentions in passing that the tests only pick up between fifty to seventy five percent of cases, which is fine, but I think a lot of people who are reading will focus on
"absolutely clear" many of those getting positive test results next week will be false positives.
and
Royal Statistical Society, too. Prof Sheila Bird, a member of the society's Covid-19 Task Force, told BBC Radio 4's Today programme false positives were "very likely

Now mathematically when the numbers are low, this may be the case, and I wouldn't dispute it. However, I suspect the lay person who reads it will come away with the idea that at all times false positive will be the majority of positive cases.

This might be good news in that people who get a positive result may then be inclined to go for the more accurate one in the hope of a false positive. However it may work the other way in that people may refuse to have it for fear of getting a false negative or if they get a positive, with no symptoms decide to ignore it because "they're sure it's a false positive".

Can I ask, without sounding mardy, why there is more focus on false positives with LFTs than false negatives, which I believed to be FAR more common : and also far more of a problem?

The ONS say 1 in 230 last week and with R still below 1 it's now going to be even less, the false positive rate reported was 1 in 250, that would mean today a positive LFT only has a 50/50 chance of being correct when it's a positive, whereas even with false negatives, it's still more than 99% correct.

Also the harm caused by a false positive is probably higher than the harm caused by a false negative right now, and if the false positive rate is too high, people will stop doing the tests.

Fortunately it looks like the false positive rate is not 1 in 250, but then that means we've not got a clue what it actually is, so can't make a sound judgement about relative harms.

I get what you mean, and my main worry has been about false negatives driving behaviour 'as if' it was a false PCR. (Narratives/messaging are important here!)

It could quite simply be that there is a 'new' angle to write about now - MRex's reasons make sense.

I basically want to know how many cases are being picked up that otherwise would be picked up too late/after infection but I appreciate that this is messy and decisions on when/whether to test vary massively.

It would be helpful if instead of Negative and Positive the LFT results were Undetected or Detected.

But is this a no,no (spelling??), scientifically speaking?

@JanFebAnyMonth

But do you remember the furore cause by Julia Hartley Brewer back in the late autumn about false positives? Completely unscientific and was corrected by Spiegelhalter. That was all before rates were this low wasn't it?

Yes, and there's a lot of risk of more misunderstanding in this area. Instinctively I believe there must be a proportion of positives among all those tests, so retesting with PCR will show 99% true positives. The false positive rate will be more like 0.5% of the positive results than 0.5% of all results. Unless it's autumn and the test can't distinguish week between different viruses, and that is important information too but can't be verified right now. If it was fine quickly then that would be really good news for shutting down the "they're all false positives" conspiracy crowd, and help make people pay attention to a positive LFT result. If I'm wrong and they are false positives, then every positive needs a PCR test for confirmation, and that should be the process.

*well not week

We really ought to be able to get a better handle on the false positive rate by following all positive LFTs up with a PCR test surely? The LFT results are instant, so no reason someone couldn't go on to get a PCR test the same day - then we actually know how many LFTs are false positives in the real world instead of having to guess from data from different places. I agree that articles telling people they may be mostly false negatives are most unhelpful, especially if they're wrong!

Thanks for the link to the saliva tests - if those come through I think that could make a big difference to uptake particularly with children and teenagers. Much easier to administer and less scope to not do the test properly.

Now mathematically when the numbers are low, this may be the case, and I wouldn't dispute it. However, I suspect the lay person who reads it will come away with the idea that at all times false positive will be the majority of positive cases.

Thanks Margaret. I think that is what I am trying to wrestle with.

This is probably a very silly question, but what causes false positives with LFT? If you did a second LFT, would your false positive still be positive, or is it a random occurance?

Is this the right way to think about false positives?

If the flase positive rate of a test is 0.3%, this means that 3 in every thousand tests would return a postive even when the person didn't have COVID.

When the rate in the community is 1 in 200, that means of every thousand tested, 8 would be positive, of which 3 would be false and 5 would be true.

But if the true rate of infection drops to 1 in a 1000, then of 1000 people tested, 4 would come back positive, of which 1 would be true and 3 would be false?

Have I got that right?

@Thenagainmaybetheydont

This is probably a very silly question, but what causes false positives with LFT? If you did a second LFT, would your false positive still be positive, or is it a random occurance?

That's what I don't really understand either, and certainly hasn't been well explained in the news articles which raise concern about the false positives. Are they random? (unlikely), Picking up some other virus? (possible?) Picking up dead Covid-19 virus from a prior infection? This definitely happens because that's why they've advised keyworkers not to use them within 3 months of having Covid, but I'm not sure this is the only reason for false positives. If it is the main reason though, it would mean the false positive rate isn't a flat rate of 0.1% of all tests, or whatever's been quoted - it would be a proportion of all positive results, so if cases fall, false positives would fall too, so not be much of a problem.

@Thenagainmaybetheydont

Is this the right way to think about false positives?

If the flase positive rate of a test is 0.3%, this means that 3 in every thousand tests would return a postive even when the person didn't have COVID.

When the rate in the community is 1 in 200, that means of every thousand tested, 8 would be positive, of which 3 would be false and 5 would be true.

But if the true rate of infection drops to 1 in a 1000, then of 1000 people tested, 4 would come back positive, of which 1 would be true and 3 would be false?

Have I got that right?

Yes, you've got that right if the false positive rate is a fixed number - eg due to some sort of manufacturing error. If it varies depending on the level of prior Covid infections then it won't always be 0.3% of all tests but might, say, be 10% of all positive results that are false because they're picking up a prior infection.

@twolittleboysonetiredmum

Primary school chn can test if they want to (households and support bubbles of too) but aren’t being done at school. Or is that starting from next week?

Not via school no, as of last Monday we can order them from the government website

@Firefliess - not just news articles; I've tried looking up research papers, MHRA, Innova statements etc - and can't find anything.

[quote MRex]@Firefliess - not just news articles; I've tried looking up research papers, MHRA, Innova statements etc - and can't find anything.[/quote]
Have just had a hunt. This seems to be where the 0.3% false positive has come from: www.ox.ac.uk/sites/files/oxford/media_wysiwyg/UK%20evaluation_PHE%20Porton%20Down%20%20University%20of%20Oxford_final.pdf

It doesn't exactly say what causes them but notes that this is an 'in the field' real world figure, and in some cases was over interpretation of marginal results, which when retested came up negative - presumably those are people with very low viral loads of who are in the final stages of shaking the virus off - importantly those rates will be proportional to the prevalence of the virus in the population being tested though, not a flat rate. The study says that the false positive rate found in laboratory testing was only 0.06%, which is quite a bit lower

We still need to understand the cause in the lab of the 0.06% though, because 5.5m 2 tests per week 0.06% is 6,600. I still think the cases will all be recovered covid or other viruses, but if manufacturing error isn't ruled out then it allows people to suggest results aren't real.