What am I missing here?
My reading of the change to PCR testing is just that IF you test positive on LFT (without having the 'classic' COVID symptoms) then you no longer need to do a confirmatory PCR, i.e. you assume you are positive and isolate without needing further tests.
That won't decrease the 'numbers', it'll just save on wasting PCR tests for cases that are already a positive. The 'cases' data (should at least) always be counting people with a new positive result, we wouldn't want two (or more) positive results from the same person on the same day to count as two cases, would we?
That won’t decrease the ‘numbers’
Yes, it will. Cases are based on PCR, not LTF, if theres less PCRs then the numbers will be less.
Yes, it will. Cases are based on PCR, not LTF, if theres less PCRs then the numbers will be less.
Unless they alter it to count both LFT and PCR?
I think the concern is how reliable is the reporting of LFT results? Of the LFTs issued, only 14% or so have been reported, although you'd think most positive results would be? Also many are sat in cupboards, not used I guess.
Just checked, it says England includes LFT in the case count unless they have a negative confirmatory lab-based PCR test taken within 72 hours.
I think the concern is how reliable is the reporting of LFT results? Of the LFTs issued, only 14% or so have been reported, although you’d think most positive results would be? Also many are sat in cupboards, not used I guess.
Of all the tests I've done I'll admit I've only bothered reporting 2. Theres not really a benefit to the individual, and if you've done one because a friend/relative/employer has asked to you do it sending them a photo of the completed test is more proof than a text/email where you could (if you were a dick) just lie about the result.
Cases on the Government dashboard are combined LFT and PCR already, for England there's even a breakdown by test type if you want to go and look at it
Cases by test type and specimen date
Number of cases (people who have had at least one positive COVID-19 test result). Cases are shown by type of test used in their first positive test and by specimen date. Positive rapid lateral flow test results can be confirmed with PCR tests taken within 72 hours. If the PCR test results are negative, these are not reported as cases. The test types shown are lab-based polymerase chain reaction (PCR), rapid lateral flow test (LFD) with positive PCR (this means the result has been verified with a positive PCR result taken within 3 days) and LFD only (no PCR taken within 3 days). People tested positive more than once are only counted once, on the date of their first positive test. Data for the last 5 days are incomplete. Some LFD results may change or be removed as more PCR results are reported.
Given that this change only applies to asymptomatic people who have tested positive on a lateral flow test and then decided to report it I don't see what difference it will make to case numbers.
Anyone who is asymptomatic and doesn't want to isolate for whatever reason either won't do a test or won't report the result, regardless of whether they have to follow up with a PCR or not. The only change it might have is to marginally inflate the case numbers because of the higher false positive rate of LFT tests compared to PCR ones.
That won’t decrease the ‘numbers’
Yes, it will. Cases are based on PCR, not LTF, if theres less PCRs then the numbers will be less.
I know that the government have done some daft things, but seriously? You really think that the intention of this change is so that they can just not count all of the LFT positives that are reported? No offence, but that seems a touch paranoid.
I can believe that there are *some* people who would do an LFT and only really consider the consequences when they get a positive, and so might then decide to chuck it in the bin and pretend that it didn't happen. But those people would have done that anyway, and not thought "well I bet that I'm *actually* negative so I'll just go and get a PCR to prove it"... There will actually be a few people who get a positive on LFT, but would have got a negative on PCR if they did a follow-up. So for those people, this change will actually artificially INCREASE the reported numbers versus the old system.
That won’t decrease the ‘numbers’
PCR tests don’t rely on people registering the result. This change will effect the total numbers of positives recorded. Anyway, it’s irrelevant. It’s not some elaborate wheeze to mess with the statistics, it’s just rationing the testing resource we have to make best use of it while prevalence is sky high.
I'm LFTing fairly regularly but don't think I've ever registered a test bar the one I needed to register to get into a cricket match.
If I tested positive I'm not sure I'd register that either, partly because I see no value in it, partly (feel free to shoot me down) as I'd likely still leave the house for a walk (alone, in a remote location) and don't want to have to explain that if someone from track and trace calls me.
PCR tests don’t rely on people registering the result. This change will effect the total numbers of positives recorded.
True, but PCR tests do rely on people booking a test and travelling to have it. Or ordering it and posting it back. I would guess that there's a large overlap between people who wouldn't report a positive LFT and those who couldn't be bothered to get a PCR.
If I tested positive I’m not sure I’d register that either, partly because I see no value in it
Worth considering if you might need to take a PCR test to travel in the next 90 days, and whether your destination will accept a record of you having had Covid en lieu of a PCR test after a recent infection.
@gray, not paranoia at all, I don't think that's the point of it, but Kelvin is right, you're taking away a cast iron way of counting positives, and relying on Joe public reporting.
Tbh it doesn't really matter, as we go with trends, rather than numbers (which are estimated to be a fraction of positives in reality).
No offence taken, as I'm not suggesting any of that, merely pointing out that it will have an effect on the numbers.
I’d likely still leave the house for a walk (alone, in a remote location) and don’t want to have to explain that if someone from track and trace calls me.
Just dont answer and when they call you again say you were in a Zwift race, call of duty death match or up to your elbows in airfix glue.
The government are ignoring positive cases anyway. It could get to a quarter of a million new cases a day, and they wouldn’t act. They’re just watching the hospitalisations and waiting. Of course, that means if any action is needed, it’ll come far too late… and I can see them using that argument to do very little even if hospitals can’t cope.
It's not taking away anything though is it?
To get to the point where you'd get one of the PCR tests that are being removed, you'd already have to have done an LF test and chosen to self report the positive result. That step remains the same, the only difference now is you don't do a PCR test too.
If you are symptomatic and so go straight to the PCR test, nothing changes.
@gray, not paranoia at all, I don’t think that’s the point of it, but Kelvin is right, you’re taking away a cast iron way of counting positives, and relying on Joe public reporting.
The only cast iron-ness that's changing is for those people who would previously have:
- done an LFT, got a +ve result, then reported it (because that's how you go ahead and get your PCR), then gone and done a PCR which came back +ve.
But now, you think that a lot of those self same people would:
- do an LFT, get a +ve result, and just chuck it in the bin.
That makes zero sense to me. The ONLY people who will now not be asked to a PCR for confirmation is those who have done an LFT and got a +ve.
This is a totally separate matter to people who are not reporting LFT negatives (probably loads and loads), and people who would get a positive but ignore it (how many of those would go to the trouble of doing a PCR that they're going to ignore anyway?)
If I tested positive I’m not sure I’d register that either, partly because I see no value in it, partly (feel free to shoot me down) as I’d likely still leave the house for a walk (alone, in a remote location) and don’t want to have to explain that if someone from track and trace calls me.
I think that's a bit uncool (mainly because, well, if everyone did that etc. etc.), but regardless, taking you as an example, if you got a +ve on LFT yesterday, would you have gone and got a PCR? Because if not, then this rule change hasn't made any difference to your case.
You report the LFT to get a PCR. If you can’t get a PCR, why are you reporting the LFT? You’ll just tell your employer and your known contacts. Why report it? Most people have turned off the contact tracing app, and the government are ignoring the number of cases… so where is the impetus to report it?
TBH, LFT +ve then PCR is kind of pointless. GAVI ran an article on the statistics of it. If you get a +ve LFT followed by a -ve PCR, statistically it will be the PCR -ve that is wrong. The higher the case numbers, even more so.
taking you as an example, if you got a +ve on LFT yesterday, would you have gone and got a PCR?
Yes.
You report the LFT to get a PCR. If you can’t get a PCR, why are you reporting the LFT? You’ll just tell your employer and your known contacts.
Correct.
TBH, LFT +ve then PCR is kind of pointless.
Except for monitoring the progress of variants in asymptomatic cases. I suppose they’re hoping that any surprises there will show up in the PCR for those with symptoms (although I fully expected this “announcement” to result in people just giving up on chasing a PCR, symptoms or not).
You report the LFT to get a PCR. If you can’t get a PCR, why are you reporting the LFT? You’ll just tell your employer and your known contacts.
I reported my LFT because I'm part of a society and I think it's useful for the government and scientists to have decent data to go on. I don't think the government are likely to make great decisions anyway, but the chances are lower if they don't have an accurate picture to base them on.
Why would you bother getting a PCR if you don't give a monkeys about anyone except yourself and your close contacts? You know you're positive anyway. The chances of an LFT being a false positive are pretty damn slim right now.
taking you as an example, if you got a +ve on LFT yesterday, would you have gone and got a PCR?
Yes.
Genuine question (I'm really not trying to be an arse, so I'm sorry if it seems that way), but what on earth for?
useful for the government and scientists to have decent data to go on
The government have made it clear they are ignoring the data as regards positive cases.
The ONLY people who will now not be asked to a PCR for confirmation is those who have done an LFT and got a +ve.
My understanding - if symptomatic you'd still go for a PCR (but why also do a LFT if properly symptomatic......my self answer is because it might NOT be Covid, a common cold *could* present similarly)
The people who don't need to go for a confirmatory PCR now are the asymptomatic where regular LFT (for whatever reason*) picks it up. You just accept that the LFT is right and act on that as a positive (or not - how people act on it of course also depends on the people)
* eg: The first time my kids tested +ve on LFT in the summer was because we were visiting my shielding parents and so we did LFT's as a family to be sure we were clean. And we weren't.
you think that a lot of those self same people would:
– do an LFT, get a +ve result, and just chuck it in the bin.
You're putting words in my mouth, please don't do that, I never said any of that.
I'm merely saying that going from PCR system which is carried out officially, recorded and counted, to a LFT system that relies on everyone reporting it themselves, the numbers can only really go down.
Is that difficult to understand?.
There's people on this thread who don't know the rules in full, and this has the advantage of some pretty shit hot people explaining stuff in laymans terms, to expect yer average Joe/Jo to report every positive case is, I think, not happening.
My understanding – if symptomatic you’d still go for a PCR (but why also do a LFT if properly symptomatic……my self answer is because it might NOT be Covid, a common cold *could* present similarly)
The people who don’t need to go for a confirmatory PCR now are the asymptomatic where regular LFT (for whatever reason*) picks it up. You just accept that the LFT is right and act on that as a positive (or not – how people act on it of course also depends on the people)
Yes, exactly right. I guess I missed 'asymptomatic' from what I wrote above. Doesn't affect my point though.
For the record I would record a positive LFT. The discussion isn’t whether you or I would, but, if taking the population as a whole, the numbers reported would be effected by people not bothering to report theirs when there is no “next step” that requires it, and seemingly little impetuous to do so.
Genuine question (I’m really not trying to be an arse, so I’m sorry if it seems that way), but what on earth for?
Because that was what the rules were as I understand it, and it seemed a not unreasonable rule to follow. The rules have now changed.
And yes, I am aware of the irony of that statement given I've said earlier I would leave the house during isolation (though again, to be clear, it would be somewhere I know to be quiet and I would visit at a quiet time).
WRT the sequencing of PCRs, only a small percentage ever were.
Depends on the region and what was being looked for, and where, at any point in time.
you think that a lot of those self same people would:
– do an LFT, get a +ve result, and just chuck it in the bin.You’re putting words in my mouth, please don’t do that, I never said any of that.
I’m merely saying that going from PCR system which is carried out officially, recorded and counted, to a LFT system that relies on everyone reporting it themselves, the numbers can only really go down.
Is that difficult to understand?.
So explain it to me, please. I genuinely don't understand how this can possibly have a significant effect on case reporting. You can pretend to be offended, and you can try to patronise me, I really don't mind.
You seem to be completely ignoring the fact that in order for an asymptomatic case detected by LFT to have been recorded in the 'old' system, the person would have had to have voluntarily sought out the PCR test, before any of that official-ness kicks in.
Why would someone who yesterday would have willingly done that (which involves self-reporting the +ve LFT), today be unwilling to do just the LFT-reporting part?
We've already had one person say that they would, so I'm genuinely curious as to why. I don't think that's because I'm terribly stupid, but I'd appreciate being educated.
I've explained
I genuinely don’t understand how this can possibly have a significant effect on case reporting.
People were told to get a PCR, to do so recorded your LFT. Now they aren’t going to be getting a PCR, many people just won’t get around to recording the LFT… you fill a form in, and seemingly absolutely nothing happens. Many people don’t tend to fill in an online form (or ring in) unless they can see something happen in the real world as a result of that reporting. The geeks will… but we’re overrepresented on this forum.
The government have made it clear they are ignoring the data as regards positive cases.
ignoring, or taking the appropriate action based on other factors - in health terms, the hospital admissions and deaths.
the first 2 waves (which I'm defining as peaking april 2020 and Jan 2021) we didn't have mass testing of the populace. there were also significantly more onerous contact restrictions. counting cases is a fairly useless metric on its own.
apart from predictions on upcoming hospitalisations - and the relationship between the two will have changed due to vaccinations - there is not a huge amount of use in knowing how many total cases there are.
Depends on the region and what was being looked for, and where, at any point in time.
Yep, and also if N is high enough even random sampling (for some reason N^0.5 + 1 sticks in my mind) is enough to be representative
eg: 100 tests = sample size 11
1,000,000 tests, 1001 is enough.
Genuine question (I’m really not trying to be an arse, so I’m sorry if it seems that way), but what on earth for?
Because that was what the rules were as I understand it, and it seemed a not unreasonable rule to follow. The rules have now changed.
And yes, I am aware of the irony of that statement given I’ve said earlier I would leave the house during isolation (though again, to be clear, it would be somewhere I know to be quiet and I would visit at a quiet time).
OK, ta. Even aside from the leaving the house part (which I do kind of get, because it's hard to feel like it's worth imprisoning yourself if you're very sure that you're not putting anyone at risk), why would one do a convoluted thing (LFT, report it, then PCR) mainly because those are the rules, but not do a slightly easier thing (LFT, report it) that is now the rules?
Feel free to consider that a rhetorical question. I'm a bit surprised that this is a contentious thing, which means that I'm obviously at least partially wrong. Again, sorry if I seem a bit argue-y, I'm not in the least bit interested in having a go at anyone for what they would or wouldn't do.
I genuinely don’t understand how this can possibly have a significant effect on case reporting.
People were told to get a PCR, to do so recorded your LFT. Now they aren’t going to be getting a PCR, many people just won’t get around to recording the LFT… you fill a form on, and seemingly absolutely nothing happens. Many people don’t don’t tend to fill in any online form (or ring in) unless they can see something happen in the real world as a result of that reporting. The geeks will… but we’re overrepresented on this forum.
That's an interesting point. Essentially saying: "do step 1 to do step 2, (then nothing much happens)" leads to greater compliance than "do step 1 (then nothing much happens)". To my (version of) logic, that seems a bit daft, maybe some psychologist somewhere might be nodding along and saying "well, OBVS".
why would one do a convoluted thing (LFT, report it, then PCR) mainly because those are the rules, but not do a slightly easier thing (LFT, report it) that is now the rules?
Because… people were told PCR were required, and useful, so they got on and went for the test. The “reporting” part of the PCR just happens… as far as the person involved is concerned (if not a geek) the test itself was the thing they were involved in, the data stuff is someone else’s concern. In fact the system sends them that data, they are passive, they don’t send it to the system. Now… take an LFT… the same person takes an LFT, it’s positive… what’s their action in the new system? It’s to stay at home and avoid passing it on. The reporting is an extra in their eyes, and likely to be missed.
why would one do a convoluted thing (LFT, report it, then PCR) mainly because those are the rules, but not do a slightly easier thing (LFT, report it) that is now the rules?
In the first instance, reporting an LFT (or a RAT as the Aussie's call then, Rapid Antigen Test) gives an outcome (an invite to PCR which may or may confirm the positive).
In the second, there is no outcome bar the data being reported. So in truth, I won't.
Edit, Kelvin puts it much better than me.
Thank you both. I guess the bit that I'm struggling with is the idea that people can buy the idea that PCR is useful and important, so going through steps to get to that (which involve effort and self-reporting) is all groovy, but yet they can't buy the idea that doing just half of that effort for the same ultimate outcome is still useful.
Maybe it would be better if it was pitched more along the lines of "if you get an LFT +ve then you must report it, then you'll be asked to report your symptoms, and then depending on the availability of PCR tests etc, you will be either asked to go for a PCR or to isolate immediately with no further testing"?
I've been reporting all my LFTs for several months now. Because it seemed like the right thing to do - we can't really complain that the government is ignoring the data if we deliberately withhold the data. I know I'm in a minority, but it takes maybe 30 seconds and isn't at all painful.
You are probably in the majority. You definitely are here on this forum. But there are millions of people would just shrug at the idea that data even matters.
You are probably in the majority. You definitely are here on this forum. But there are millions of people would just shrug at the idea that data even matters.
I don't know anyone reporting negatives, and that includes a fair number of people who work for the NHS.
I've reported all (except maybe one where I forgot) of my negatives; I don't think my wife has reported any of hers. To me, not reporting a negative is much more understandable than not reporting a positive.
It's a bit open to abuse for those who fancy a bit of shirking. We have to provide photos of negative LFTs to go to work. If positive we'd need to have a PCR and show the NHS evidence email. I don't know if my employer will/can enforce a PCR given the new guidance. I could just send a photo of my wife's positive LFT and return to work seven days later with a negative LFT.
I don’t know anyone reporting negatives, and that includes a fair number of people who work for the NHS.
I misread, I didn't realise they meant they were reporting negative LFTs. My fault, they were clear in the post. My youngest and my other half have been reporting theirs (both in schools). My eldest hasn't (Uni). I haven't reported a single one of mine (working from home). I agree it's likely only a minority that are reporting all their negative tests. Maybe even a vanishingly small minority.
In my mind the danger of dropping the PCR test is that true figures of positive cases will drop.
Track and Trace, or whatever it’s called this week, only kicks in when you have a PCR test, the reporting happens, it’s the system that does that, not the individual.
Now the people that test positive on a LFT are asked to report it, if that person wants to ignore that result because they are selfish, ignorant, don’t want to isolate, etc. Then there’s no official record of that test having taken place. No official result, no Track and Trace. Nothing. They are free to wander and spread without any official records.
Also, there’s now zero chance of any data about variants cropping up through testing of your PCR, however small that was in reality.
Incidentally, my work have now reintroduced the isolate if a household member has tested positive. Prior to the Christmas shutdown they were following government advice, you’re free to come to work if double jabbed, even though you are pretty likely to be a few days away from a positive case. I banged on for months about how stupid it was to deaf ears.
