If your child has a +ve lateral flow test in school they will have to isolate even if they later pass the full PCR test

[CatOnAHotTinHoof]

www.theguardian.com/education/2021/mar/06/school-covid-tests-pupils-in-england-very-likely-to-get-false-positives
I would have thought that if they pass the full PCR test that would supercede the lateral flow test and they could return to school.

@mightyducks

If they’re done at school, that counts as a testing centre and no PCR will be needed, any test done at home though will need a confirmatory PCR test to be a true ‘positive’

But if a confirmatory test IS done (even if not necessary) why is the PCR result not taken into account.

Surely if it overrules a home done lft it should,also overrule a school done one (both are done by the child but with an adult watching) - the school staff didn't do them for them.

I have ti say I'm.a but concerned about this.

I gave us all covid tests when dd2s bubble closed. We all tested negative. Dd2 hasn't been anywhere since mid December if I had to put money on one person in the house not having covid it would be her. I am.pretty worried about false positives as that means 2 weeks at home for both dds having only just had a negative test 2 weeks ago ajd her not having been anywhere to catch it.

If I’d known a bit more about this I probably would have questioned DS’s school first before giving consent.

It’s easy enough to order the LFT or collect if you have a site near to you.

I just find this completely nuts!

@Whatwouldscullydo

I have ti say I'm.a but concerned about this.

I gave us all covid tests when dd2s bubble closed. We all tested negative. Dd2 hasn't been anywhere since mid December if I had to put money on one person in the house not having covid it would be her. I am.pretty worried about false positives as that means 2 weeks at home for both dds having only just had a negative test 2 weeks ago ajd her not having been anywhere to catch it.

it is a definite concern as PPs have said. However overall I think it's still very very unlikely.

The LF tests can pick.it up from.months ago to though can't they? So someone who was exposed back then will.have to isolate again even though they already did.

Because the DHSC changed the rules a-few months ago , once they had more data on the rate of false positives for LFD’s done in testing sites , these are extremely rare, approx 0.001 %, when people say they aren’t accurate, it’s the false negative rate which is really high. LFD’s are good at picking up people with high viral loads, therefore highly infectious, not good at low viral loads. In my experience of working with settings and businesses where they have been implemented , they have picked up people a good 24-48 hours before they have started with symptoms, very very few people who were completely unsymptomatic.

@Whatwouldscullydo

The LF tests can pick.it up from.months ago to though can't they? So someone who was exposed back then will.have to isolate again even though they already did.

No that’s the PCR tests

Then why does it say when booking the test that you cant do it after day 5 on the postal?

@Olivia333

They’ve just spoken about this on the Andrew Marr show and somebody from public health England has confirmed that it’s not recommended to get a PCR test with positive results from the LFT in secondary schools

What possible reason is there for this advice, other than to avoid the issue at hand here - the fact that pupils and families will be isolating unnecessarily and rule change is needed that the government is avoiding making.

Cleary a less accurate test should be outweighed by a more accurate test.

At our school, the invalid tests have to do them again.

@Whatwouldscullydo

Then why does it say when booking the test that you cant do it after day 5 on the postal?

Presumably you mean a postal PCR should not be ordered 7 days after symptoms have started? That’s a different issue with the reliability of the testing 7 days after the symptoms have started ,and as the postal testing takes longer to reach you and then lost back, they advise you to go to a testing centre, as after that time the accuracy of the tests declines

Thanks

All this concern and talk about false positives what about false negatives?!
DS secondary school have conducted nearly 2000 tests this week (staff and pupils). All tests were negative. No invalid result and no positive. This has made me question there accuracy. Rightly or wrongly I’d have expected at least one negative/invalid result! Maybe I’m more sceptical because of experience at DP primary school. A few weeks ago a staff member tested negative on LF test in the morning. It was a regular testing day but she did had a sore throat. Two days previous a child in her bubble was unwell and at home awaiting test results. That afternoon staff member developed a temperature,went straight home and booked a PCR test. Next day unwell child’s test was positive so bubble was shut down and the following day the staff members pcr test said positive. 2 known parents in the following 2 weeks tested positive,no other children. So the LF test of the staff member in the morning was negative but the PCR was positive in the afternoon! Staff member still unwell and not back to work yet.

Being concerned about false positives is a separate issue to concern about false negatives, and indeed a person can be concerned about both at the same time.

A false positive is easily verified by a more accurate PCR test, which is the issue here. Why not verify with a more accurate PCR test and isolate/not isolate on that basis?

The problem of a false negative is not so easily rectified, so why compare the two? I am also very concerned about false negatives, but there doesn't seem to be an easy solution for these.

The fact remains that it is easily to verify a false positive and overruling a false positive LFT with an accurately negative PCR should be possible and allowed.

I quite agree false positives and false negatives are separate problems however there is no talk in the media or on here about the latter.

I am actually surprised by the lack of media attention to false positives, given how detrimental it will be to those affected, their families and their close contacts who will all be told to stay inside for 2 weeks. I have only seen the Guardian article - not normally a paper prone to sensationalism. I wonder why none of the Tory media outlets are talking about this?

As to false negatives, the only way to fix that is to get more accurate tests into school, which may happen one day, once the government has used up its vast stock of inaccurate test kits already purchased

This is craziness.

LFTs at school do not need a PCR test follow up and any negative PCR test that follows will not count. This means that a pupil and family all still need to isolate for 10 days purely as a result of the LFT 😳🤦‍♀️

I am considering not consenting to school LFT for this reason and instead will do the tests at home.

@CKBJ

All this concern and talk about false positives what about false negatives?! DS secondary school have conducted nearly 2000 tests this week (staff and pupils). All tests were negative. No invalid result and no positive. This has made me question there accuracy. Rightly or wrongly I’d have expected at least one negative/invalid result! Maybe I’m more sceptical because of experience at DP primary school. A few weeks ago a staff member tested negative on LF test in the morning. It was a regular testing day but she did had a sore throat. Two days previous a child in her bubble was unwell and at home awaiting test results. That afternoon staff member developed a temperature,went straight home and booked a PCR test. Next day unwell child’s test was positive so bubble was shut down and the following day the staff members pcr test said positive. 2 known parents in the following 2 weeks tested positive,no other children. So the LF test of the staff member in the morning was negative but the PCR was positive in the afternoon! Staff member still unwell and not back to work yet.

😳 that is shocking

It sounds like we did the right thing not to take DC for school LFTs.

it is a definite concern as PPs have said. However overall I think it's still very very unlikely

The Porton Down / Oxford report on the LFT tests report a 1 in 250 false positive rate outside of the lab (so in a school or at home), with around 25 weeks left in the school year, that means each kid taking 2 a week will test 50 times.

That means the chance that an individual will get a false positive is possibly 50/250 or 20% of all kids will and therefore need to isolate.

We don't actually know that all the tests are independent, it could be that they're not and having a previous false positive increases your chance, if they're not independent then for some kids it will be much higher than 20%.

There's also some doubt on the PHE data itself and the false positive rate may be different, but that is the best evidence available today.

@sirfredfredgeorge
Those stars are indeed worrying but I’m sure that a false negative is far more likely than a false positive.
I saw a friend today who works in a 3000 kid high school. They have ALL had at least 1 test at the end of the week (at least 5,000 tests) and not had a single positive yet. We’re in a relatively high risk area too.

Those stars are indeed worrying but I’m sure that a false negative is far more likely than a false positive

A false negative is much more likely in the sense that the test getting it wrong and saying you're negative when you're actually positive. But overall until the prevalence changes massively because you're way more than 200 times more likely to be negative the actual expected number of wrong results biases towards the false positives.

If the prevalence was a lot higher it would go the other way of course, but the only weeks where that would've been the case so far is the last few weeks of the December term, and lockdown immediately followed, so we're a long way until we get to those levels unless something very different happened.

So it has been clarified by the powers that be, a negative PCR overrides a positive LF.

And yes you will get a lot of false negatives. I work in a maternity unit in London and I had a positive lateral flow followed by positive PCR - was very ill. A short while later two colleagues had pos LF and neg PCR (back to work, asymptomatic). Two colleagues have had neg LF and pos PCR whilst symptomatic.
It’s not accurate at all, but it is damage limitation

@Mummyme87 that’s only home tests; it won’t overrule a school LFT positive