Coronavirus - The Thread :(

[varesecrazy]

That is beacuse they insist on calling every positive test now a "case" whether it is a real positive, whether the person involved has no symptoms or some symptoms or severe symptoms.

Thats fine by me..
everybody who carries the virus.. and is then capable of spreading it is counted

I was relating last weeks levels as

66% in England and 75% in Wales

Wales is now 100%
England 1..err..hundred and.. twenty five.?
Fifty..??

If they had graded 1 to 10
and equated to the hundreds per 100,000 it would have been A LOT more ledgible

BUT no doubt the GOV'T are loading rates of spread etc in their tier strategy

 

[StevenRB45]

There is quite a bit of weird nonsense going round with the stats...a guess would be it's R number related!

I spent all of November being extremely careful as having tested positive regardless of how I died I'd have died of Covid. So if I fell down the stairs 22 days after testing positive once I'd fully recovered...still would have been a Covid death.

 

[pooroldcodger]

The R rate that we keep hearing so much about is a statistical guess based on positive tests, numbers of deaths, whether the area they are looking at has schools open or shut etc etc etc. It is not some sort of cast iron figure . So if we have tests that are false positives (and we know that we do have a lot of false positives because the tests that they are using are not designed for how they are being used, and lots of untrained people are carrying out the tests, and we are carrying them out on an industrial scale) then these false positives will for certain be having an impact on the R rate.

 

[pooroldcodger]

Thats fine by me..
everybody who carries the virus.. and is then capable of spreading it is counted

I was relating last weeks levels as

66% in England and 75% in Wales

Wales is now 100% England 1..err..hundred and.. twenty five.?
Fifty..??

If they had graded 1 to 10
and equated to the hundreds per 100,000 it would have been A LOT more ledgible

BUT no doubt the GOV'T are loading rates of spread etc in their tier strategy

That's the point - not everybody that is testing positive IS carrying the virus.
It has been suggested by much cleverer peolle than me that in medicine if you have an inication of something being wrong then you look further and check again. So we should be following up a positive test with another test soon after to check. This is important because so much is now hanging on these test results.

 

[varesecrazy]

Tests performed by 'untrained people'

Not too big a stretch..

as you get passed the bag through the car window.. park up in a quiet spot..
'Have a go..'
then drop it into the 'cool box' on your way home

Doesnt everybody..?

 

[jrkitching]

That's the point - not everybody that is testing positive IS carrying the virus.

:yeahthat:

And if the average infection rate in the area being tested is low, and you test the general population at random, then even if the test only has a 1% false positive rate, almost everyone who tests positive won't have the virus.

This is counterintuitive, but true.

Confused? I'm not surprised.

To make any sense of the statistics, you need a good understanding of Bayes theorem. If you're not familiar with this, there are a whole host of explainers who've made youtube videos; this is my favourite:

https://www.youtube.com/watch?v=lG4VkPoG3ko

 

[AndyRKett]

If I perform 1000 tests on 1000 people then it’s likely that some of those tests might not go correctly.

So it’s reasonable to assume if some tests are not done properly you won’t pick up on what is needed to produce a positive test result despite someone being positive (what’s known as a false negative)

Now if I’m really bad at testing I could rack up loads of tests where I’ve don’t them badly and not manage to get the swab in the right place producing lots of false negatives.

However it is unlikely by doing my job incorrectly that I would put a swab in someone’s nose and come up with a positive result when they are not. Maybe if I contaminated the sample from a different patient or if i put the swab in a packet under the wrong name then it might be possible to show a positive result when someone isn’t.

Basically you’re likely to get many more false positives than false negatives the more untrained and badly performing the staff the less likely they’re to fund the positive cases.

So actually if someone is negative they’re more likely to need testing some more than someone who is positive, as if you’re positive then you’re more likely to be positive


The R rate as a number is pointless. If you assume you have one person is positive the. They infect one other person then the R number is 1.

It doesn’t have to be 1 it could be 1,000 if 1,000 people infect 1,000 other people then the R number is in effect still 1 to 1 anything less than one is desirable as 1 or above means nothing is getting better if the R rate is 0.999 then that means 1000 people would infect 999 and therefore each generation of infection the number of infected would decrease.

The number of deaths is irrelevant to the R number it is only based on the number of infected versus the number of people who then got infected.

If I was the only person the whole country infected but I infected two other people then the R rate would be 2. If I infected 3 then the R number would be 3. Me infecting 3 people is hardly going to bring a whole country to it’s knees by us when the number of infected is 40,000 and the R number is 1.01 that means the next generation of people who gets infected is 40,000 +another 40,400. And just like that you have some 80,000+ people infected so the R number mustn’t be 1 is MUST !! Be less the. 1 and the lower below 1 it is the quicker we will get rid of the virus. People seem to think that 1 is the target and if we have an R number of 1 or “near” 1 everything is fine. This is an absolute fallacy and people need to just keep away from one another and the number would go down

 

[MrMagoo]

A month ago, I had Covid-19. I was tested on a Thursday and on Friday got a positive result. On partner had a test on Wednesday (day before my test) and got a negative result on Thursday. We did all the things a couple do prior to my test. I had all the symptoms on Thursday but not before.
By my reckoning I did not have Covid-19 before Thursday.
I was very ill but my family had no symptoms whatsoever.
The Covid-19 consultants (Doctors) thought when we catch it, our immune system keeps it in check, but I had a back injury the same week which compromised my immune system. They weren't sure if I was asymptomatic before I tested positive.

 

[jrkitching]

So actually if someone is negative they’re more likely to need testing some more than someone who is positive, as if you’re positive then you’re more likely to be positive

That's certainly true for rapid lateral flow testing; in untrained hands, sensitivity is less than 60%, so a single test alone will identify less than six out of ten people carrying the virus. Even when administered by trained laboratory specialists, it's still under 80%. Trained front line healthcare staff manage about 73%.

https://www.bmj.com/content/371/bmj.m4469

From that article:

“The poor detection rate of the test makes it entirely unsuitable for the government’s claim that it will allow safe ‘test and release’ of people from lockdown and students from university,” he warned. “As the test may miss up to half of covid-19 cases, a negative test result indicates a reduced risk of infection but does not exclude covid-19."

 

[dave]

If I perform 1000 tests on 1000 people then it’s likely that some of those tests might not go correctly.

So it’s reasonable to assume if some tests are not done properly you won’t pick up on what is needed to produce a positive test result despite someone being positive (what’s known as a false negative)

Now if I’m really bad at testing I could rack up loads of tests where I’ve don’t them badly and not manage to get the swab in the right place producing lots of false negatives.

However it is unlikely by doing my job incorrectly that I would put a swab in someone’s nose and come up with a positive result when they are not. Maybe if I contaminated the sample from a different patient or if i put the swab in a packet under the wrong name then it might be possible to show a positive result when someone isn’t.

Basically you’re likely to get many more false positives than false negatives the more untrained and badly performing the staff the less likely they’re to fund the positive cases.

So actually if someone is negative they’re more likely to need testing some more than someone who is positive, as if you’re positive then you’re more likely to be positive


The R rate as a number is pointless. If you assume you have one person is positive the. They infect one other person then the R number is 1.

It doesn’t have to be 1 it could be 1,000 if 1,000 people infect 1,000 other people then the R number is in effect still 1 to 1 anything less than one is desirable as 1 or above means nothing is getting better if the R rate is 0.999 then that means 1000 people would infect 999 and therefore each generation of infection the number of infected would decrease.

The number of deaths is irrelevant to the R number it is only based on the number of infected versus the number of people who then got infected.

If I was the only person the whole country infected but I infected two other people then the R rate would be 2. If I infected 3 then the R number would be 3. Me infecting 3 people is hardly going to bring a whole country to it’s knees by us when the number of infected is 40,000 and the R number is 1.01 that means the next generation of people who gets infected is 40,000 +another 40,400. And just like that you have some 80,000+ people infected so the R number mustn’t be 1 is MUST !! Be less the. 1 and the lower below 1 it is the quicker we will get rid of the virus. People seem to think that 1 is the target and if we have an R number of 1 or “near” 1 everything is fine. This is an absolute fallacy and people need to just keep away from one another and the number would go down

glad you posted this, was doing my nut in all these people claiming false positives, false negatives very easy to understand, but false positive it had to pick up the virus on the test from some where.
Its like home pregnancy kits often hear of people not doing them right and thinking they are not pregnant when they are because they didn't read the instructions properly, dont think ive ever heard of one saying some one is pregnant when they wasnt, does that happen?

 

[jrkitching]

glad you posted this, was doing my nut in all these people claiming false positives, false negatives very easy to understand, but false positive it had to pick up the virus on the test from some where.

The chances of a false positive are much, much less than the chances of a false negative. The lateral flow test has only a 0.32% chance of giving a false positive result; that's less than 1 chance in 300. The chances of a false negative with this test can be almost 50%.

But - and here's the thing - even with a test that has less than a 1 in 300 chance of giving a false positive result, if you test the symptomless population at random, most of those who test positive won't actually have the virus.

So a bunch of folks saying they've had a positive test but not gone on to develop Covid is actually what you'd expect.

This is when statistics looks weird; you have a test which has a 99.7% probability that a positive result is accurate, yet most of those who test positive don't actually have the virus.

...dont think ive ever heard of one saying some one is pregnant when they wasnt, does that happen?

It's rare, but it happens. There are a number of drugs & medical conditions which can also elevate hCG levels.

 

[pooroldcodger]

glad you posted this, was doing my nut in all these people claiming false positives, false negatives very easy to understand, but false positive it had to pick up the virus on the test from some where.
Its like home pregnancy kits often hear of people not doing them right and thinking they are not pregnant when they are because they didn't read the instructions properly, dont think ive ever heard of one saying some one is pregnant when they wasnt, does that happen?

From what I have heard and read from several different "experts" the pcr test (I think it's called) is very sensitive and can pick up "bits" of old virus which are not any longer infectious but will still return a positive result.
But as has become clear this is a very complicated subject and what is certain is that cool and calm heads are required from the top.

 

[portland_bill]

... and what is certain is that cool and calm heads are required from the top.

We're doomed!

 

[jrkitching]

But as has become clear this is a very complicated subject

Indeed it is. Most folks don't understand how the mathematics of population screening actually works. Even when the chances of a test giving a false positive result are extremely small, most folks who are tested and receive a positive result won't actually have the disease.

So, let me present JR's Covid testing guide for dummies:

If you are symptomless, have a random Covid test, and the test gives a positive result, then:

1) It's more likely than not that you don't have Covid (so don't overworry), but

2) It's absolutely vital that you self isolate for the prescribed period. Assuming an infection rate of 100 per 100,000 people (about right for where I live at the time of writing), your chances of having Covid after a positive result have just gone up from about 1 in a thousand to about 1 in 3.

In statistical terms, testing updates the prior probability of your having the disease, so its predictive value for a specific result depends both on the accuracy of the test, and the prior probability of the person being tested (essentially the prevalence of Covid in the sample of the population you are testing).

All this only applies to testing if you are asymptomatic. If you have another reason to suspect you may have Covid before taking the test (like having one or more symptoms), then the likelihood of your having Covid if you get a positive result increases dramatically.

I wonder how much the politicians actually understand?

However, the scientists who are advising them will know all this. I feel sorry for the scientists who have to explain the theory to the political leaders; it will likely be a nightmare to get the politicians to understand what is obvious to them.

 

[pooroldcodger]

Indeed it is. Most folks don't understand how the mathematics of population screening actually works. Even when the chances of a test giving a false positive result are extremely small, most folks who are tested and receive a positive result won't actually have the disease.

So, let me present JR's Covid testing guide for dummies:

If you are symptomless, have a random Covid test, and the test gives a positive result, then:

1) It's more likely than not that you don't have Covid (so don't overworry), but

2) It's absolutely vital that you self isolate for the prescribed period. Assuming an infection rate of 100 per 100,000 people (about right for where I live at the time of writing), your chances of having Covid after a positive result have just gone up from about 1 in a thousand to about 1 in 3.

In statistical terms, testing updates the prior probability of your having the disease, so its predictive value for a specific result depends both on the accuracy of the test, and the prior probability of the person being tested (essentially the prevalence of Covid in the sample of the population you are testing).

All this only applies to testing if you are asymptomatic. If you have another reason to suspect you may have Covid before taking the test (like having one or more symptoms), then the likelihood of your having Covid if you get a positive result increases dramatically.

I wonder how much the politicians actually understand?

However, the scientists who are advising them will know all this. I feel sorry for the scientists who have to explain the theory to the political leaders; it will likely be a nightmare to get the politicians to understand what is obvious to them.

I am sure a lot of the scientists do understand this, and I am more than sure that the politicians don't.
But the Sage committee also has plenty of behavioural psychologist types as well as the famous mathematical modeller on board tok so I do have some sympathy for the politicians in that they must be being pulled in all directions.
I exempt Hancock though who I have no sympathy for whatsoever.
But I shouldn't think he will lose any sleep over my opinion!
Happy Christmas everybody.

 

[09 johno]

I see the Oxford-AstraZeneca vaccine has also been approved in the UK. It requires 2 doses 12 weeks apart and is be kept at normal fridge temperature which means distribution will be a lot easier. vaccination program will start next week with 100,000,000 doses on order (enough for 50,000,000 people) at least it is being manufactured in the UK so transportation should be easier.

 

[jrkitching]

Another big advantage with the Oxford vaccine is that it can be administered in pharmacies, in much the same way as the flu jab. Being able to deliver the vaccine via an existing, established, tested distribution channel outside of mainstream primary care is a huge plus point.

I went to Boots for my flu jab this year; whilst administering it, the pharmacist said they (Boots) were already preparing to deliver the Oxford vaccine in the same way; they were just waiting for approval from the regulator.

 

[09 johno]

I am guessing that this vaccine will be annual like the flu jab, at least for the most vulnerable once the virus is under control properly and at £3 a dose is at a reasonable cost

 

[jrkitching]

I am guessing that this vaccine will be annual like the flu jab, at least for the most vulnerable once the virus is under control properly and at £3 a dose is at a reasonable cost

We don't yet know how long the vaccine will provide immunity; an annual revaccination is probably more likely than not.

Covid will be with us for the forseeable future, and there'll be mutations, so they'll likely need to update the vaccine each year, just as with the current flu jab.

I've no idea if this is technically possible, but I'd have thought that, going forward, they'll just bundle the two together.

 

[Pugglt Auld Jock]

I see the Oxford-AstraZeneca vaccine has also been approved in the UK. It requires 2 doses 12 weeks apart and is be kept at normal fridge temperature which means distribution will be a lot easier. vaccination program will start next week with 100,000,000 doses on order (enough for 50,000,000 people) at least it is being manufactured in the UK so transportation should be easier.

Sounds like good news doesn't it - and I really hope it is. However I've heard some commentators saying that the intention now is to try to get a first jab into as many people as possible - which, if I've picked up on it correctly - gives sufficient stimulation to most people's immune system to stave off the worst reactions. So it prevents the hospitals being overwhelmed but isn't going to stop many from becoming unpleasantly unwell. Only when as many as possible have had their first jag will attention then be turned to delivering the second "booster" jag. I wonder if it will be delivered in the time frame recommended and if not, I wonder if the final level of immunity is compromised?

We haven't been over our doorstep for the last 10 days and realized last night that supplies were running low. Decided to do a supermarket run today as we thought tomorrow, being new year's eve, might be busier. We just shop at our local supermarkets and haven't found them crowded at all. Went to our usual Lidl and it was just a little more busy than we've seen before so, with masks and gloves on, we didn't hang about and did a sort of "supermarket sweep" being out again in under 20 minutes. What was very noticeable today, which we haben't really seen before, was a fair few folk not wearing masks. As we walked in, a young man walked round us with no mask. Almost immediately an elderly couple, probably in their mid to late '60's, walked across in front of us. We saw at least another 4 people during our visit who weren't wearing masks. We've not run into this before, are people just getting to fed up with it all to bother? Staff were not challenging these people.

Quite a lot is being said about the likely effects of the Christmas mixing which (to my mind, inexplicably) was allowed. But I feel considerable dread over what Hogmanay may bring - remembering that new year celebrations have always been a very big "thing" up here.

As said above, I think it very likely the covid jag will become a yearly event, like the flue. We noticed this year (having read the wee leaflet they hand you after your flue jag) that it covered several strains, including Flue "A" which nearly did for Mrs J last year when it degenerated into pneumonia! So I wouldn't be surprised to find they can make a one jag cocktail with the conventional flue jag?

Although I'm just a little worried about the safety of these new covid jags because of the speed at which they have been developed and so maybe something has been "missed" Mrs J and I will be running to the head of the queue when they say we can have it!