Lateral flow tests do they work?

[Trollsinthedungeon]

I did one on Sunday because I felt grotty and I was meant to be in work on Monday, I have to do them 2x a week. I tested negative. Had an asthma attack that night got rushed to hospital treated and then tested for covid because I had 2 out of 3 symptoms.

That PCR test was positive

My truest have actually stopped using them in the last couple of days because of the high level of negative results, they decided to check them with pcr tests and there was a huge increase in positive because the lateral flow didn't pick it up.

that is very interesting. I have them for work, also testing twice a week. dd recently lost her sense of smell and as I have spare tests (due to being on A/L) I used one for her. There was a VERY faint positive line. So faint I initially missed it and dismissed it as negative, then as I went to put it in the bin I noticed the vv faint line. She then did a second lateral flow test which came back negative, followed by a positive pcr test. I now feel generally unwell, but no specific symptoms, but lateral flow is negative - so who knows!

@junglepie very interesting I also had an extremely faint line on a test last week before the symptoms started but work work asked me to discount it because I had noticed it outside of the 30 min window 😂

I’m also wondering this. I have no symptoms but dh friends exchanged Christmas presents last Wednesday and turns out they have Covid . I’m trying to work out the chances of me catching it if dh friends had masks on the only exposure to the virus was from the cloth bag which I forgot to wash my hands after touching. Lateral tests are coming back negative

To add dh friends were standing outside. What tests are taken at drive through centres that come back within 24 hours

I did 3 lateral flow tests at work last Sunday (nhs staff) all negative. Positive PCR came back the next day...I'm dubious about their usefulness if I'm honest.

Lateral flows miss up to half of all positive cases. So no, they don't really work. And are no substitute for isolating from a known PCR confirmed case. Now if someone can tell the Gov that....

We have 180 people in the department we work with covid patients doing aerosol generating procedures every day. Not one person has tested positive using lateral flow tests

I guess they have their place for mass screening of asymptomatic people but definitely not where a negative that should be a positive would be a disaster.

I saw some stats that showed they're quite effective when used by trained healthcare professionals and pretty ineffective when used by lay people. Nowhere near as effective as the other type of tests.

We were told today they think they are 75% effective and have been picking up cases. If you have any symptoms though you should be getting a proper PCR test anyway.

They've now picked up 3 cases in my small team, all confirmed by PCR. One remains asymptomatic, two have gone on to develop symptoms post-test. All would have been in seeing patients in the interim, were it not for the lateral flow.

As I understand you have to have to have a “high viral load” for them to pick up a positive. So many asymptomatic people will not register positive. Symptomatic people far more likely to have a higher “viral load”

Not designed for asymptomatic people so little wonder they are so unreliable.

@Motorina
Pleased to hear this.

@ChristmasBubble

I saw some stats that showed they're quite effective when used by trained healthcare professionals and pretty ineffective when used by lay people. Nowhere near as effective as the other type of tests.

And when children do it on themselves - utterly useless....

The studues I've seen have shown they are most effective when done by laboratory staff, followed by health care staff. I do think that both the administering AND the reading of the results needs some level of skill. For comparison these are the tests I did on my dd (14) The first one on the right shows a vvv faint line. The second one on the left had no line. PCR Was positive. Her only symptom was loss of smell.

So using them in schools, self administered by the students, to replace isolation of close contacts, is this a bad idea?

BMJ was pretty scathing - although accuracy is over 90% in the hands of lab staff, it drops to just under 80% when carried out by other HCPs and under 60% when done by trained members of the public.

@EndoplasmicReticulum

So using them in schools, self administered by the students, to replace isolation of close contacts, is this a bad idea?

I doubt you could have come up with a worse one if you'd tried.

Unless aim is to have it spread rapidly in schools and vulnerable staff and household members if pupils are acceptable collateral damage.

They are not recommended for symptomatic cases so if you had two out of three symptoms you should have been getting a PCR test.

No one has ever said they are highly effective. But when it comes to general testing they are a way to pick up more asymptotic cases than just doing nothing. This is why airlines/countries often require a PCR test rather than relying on lateral flow.

No one has ever said they are highly effective.

Gavin Williamson has. My headteacher has.

But when it comes to general testing they are a way to pick up more asymptotic cases than just doing nothing.

Agreed. But in schools they will be used instead of self-isolation. Reckless.

In the Liverpool mass testing did they not only pick up 50% of cases? Doesnt sound very effective

In Birmingham they got a massive 3%
www.newscientist.com/article/2263746-test-caught-just-3-per-cent-of-students-with-covid-19-at-uk-university/

There are different lateral flow tests and it matters which one we are talking about. The one the govt used in the Liverpool mass testing is by Innova. There is also a lateral flow test by Roche which apparently is much better.

The stats you read also need careful interpretation. For example some of the stats give false negative rates for asymptomatic people. You have to work out if they mean people who will never have any symptoms or presymptomatic people who just didn’t have symptoms at the time. As ever it really needs an expert to understand.

I work in the nhs. 2 members of unit staff (with temp & cough) both tested positive on the lateral flow test, then both positive PCR test.

This is an interesting thread considering Gavin Williamson has been everywhere this morning saying how reliable they are.

They are not. Especially when self-administered by children.

To use them in schools from next week to replace self-isolating for close contacts of positive cases is reckless and far less safe than the original plan. I will NOT be consenting for my children to do this-they can continue to self isolate and work remotely for 10 days. I’m just pissed off not all parents will do this which will put all children, staff, parents and the community at risk.

Would you want your child on the bus with, sitting next to, or being taught by someone all day who is positive but the test is so faulty, it hasn’t picked it up yet?

I expect this to make the situation far far worse in schools, then the community, and will end up causing UK cases and deaths to rocket.

That will close schools, not keep them open.