Anyone else get false positive LFTs? Worried about the new rules' impact on time off work

[LFTquestion]

DH repeatedly gets false positive LFTs (later negative PCRs). This is the fourth time now, and we are really fed up. Each time it requires a couple of days off work while he waits for the PCR results. It has happened pretty much every month since October.

He is triple jabbed and has never had Covid (that we know of!).

However, from next week, if he gets a positive LFT while asymptomatic, he is presumed to have Covid and will have to have a week off work.

But clearly, the odds are that these positive will be wrong!

He is a key worker and taking one week off every month isn't sustainable. He has to do LFTs twice weekly and provide proof of them to work, so simply not doing them isn't an option.

Has this been happening to anyone else? What's the plan??

I have the same issue with FlowFlex tests. Positive lateral flows followed by negative pcrs. This has happened multiple times since October.
I’ve managed to get hold of a different brand of lft because I can’t afford to have time off work to wait for a pcr if I take another FlowFlex.

@LondonQueen

False positives are usually a result of not following the instructions carefully or contaminants in the test sample. You need to wash your hands, wipe down the surface and blow your nose before taking a test, you're not supposed to eat or drink within 30 minutes either. Never had a false positive.

There's something more going on here than wiping down the surface etc. The contamination risk presumably relates to introducing Covid from another source such as a surface or a finger, which is incredibly unlikely, especially in your home. You'd have to have someone positive cough onto a surface, you wipe your finger along it, and then rub the end of the swap with your "dirty finger".

@vickyc90

Does he have reflux by any chance? Was talking to my gastro consultant about masks making it worse and he asked if I was getting false positive LF's aswell.

Yes he does!

Can you tell me more please?

I have just checked and we’re using FlowFlex, interesting…

I kept getting positives and noticed that if I vape before taking the test I got faint positive. Now I leave half an hour between and get negatives.

@LondonQueen

False positives are usually a result of not following the instructions carefully or contaminants in the test sample. You need to wash your hands, wipe down the surface and blow your nose before taking a test, you're not supposed to eat or drink within 30 minutes either. Never had a false positive.

My daughter has had them on 3 separate occasions. Multiple times - with one brand of LFT.

So no, it’s not always user error and happens so often that I think those tests are flawed

@LFTquestion

I have just checked and we’re using FlowFlex, interesting…

And yes, they’re Flow Flex!

I’ve reported them to MHRA on their yellow card reporting. If enough people report then they may actually listen ffs.

I had my first false positive this week and it was on a flowflex. It was just outside of the 30 minute time window, but hasn’t happened with any of the many others I’ve done.

Lateral flow tests for COVID-19 can be very accurate and specific when used as directed, but introducing acidic fluids can cause the tests’ detecting antibodies to clump, which may read as a positive result.
www.the-scientist.com/news-opinion/sodas-lemon-juice-cause-false-positives-in-rapid-covid-19-tests-68965

Reflux would give the acid environment.

That's so interesting a consultant mentioned about reflux. I had wondered if that could be a possibility for DS - perhaps he is particularly acidic in the mornings? We normally test in the evening, but the 4 times we have tested him in the morning, it has been positive. He has never said he feels uncomfy, but I will ask him about his tummy now....

@Postdatedpandemic

Lateral flow tests for COVID-19 can be very accurate and specific when used as directed, but introducing acidic fluids can cause the tests’ detecting antibodies to clump, which may read as a positive result. www.the-scientist.com/news-opinion/sodas-lemon-juice-cause-false-positives-in-rapid-covid-19-tests-68965

Reflux would give the acid environment.

Thank you for that. Very interesting. So my theory that something other than Covid is causing the positive result is not totally daft.

However I don't get reflux and I follow the instructions to the letter. Worthwhile knowing though.

I have been getting false positives on Flowflex tests too and I have reflux. If I test early in the morning it is a stronger fake positive, the line is paler later in the day. I have had 2 PCR tests to confirm and can thankfully work from home.

@ConcernedAuntie there's a whole worm hole of nasal pH to be explored pubmed.ncbi.nlm.nih.gov/10196653

I've had 4 'false positives' on the old style lateral flows, all in the last 3 weeks. The new style ones have always been negative.

wow, great just great...literally every third person in the world suffers with reflux (be it known to them or the silent variety). This is like playing Russian roulette. Imagine all those false positive cases isolating + close contacts testing or isolating for absolutely no reason! No wonder the NHS and all other services are on their knees and it'll only get worse after Tuesday next week. Now that they haven't got deaths to report on, let's keep bumping up the numbers with asymptomatic cases!!
This is an utter joke and all majorly f$^%ed up BUT who cares?! Here in the UK we love "living" like this!!

Yes to my mum today, positive lateral flow but negative pcr. She had cold symptoms

"However, from next week, if he gets a positive LFT while asymptomatic, he is presumed to have Covid and will have to have a week off work. "

No he won't.

The rules will be that you don't have to do a PCR if you get a positive on a LFT but you won't be stopped from getting a PCR. So if he gets a positive on a LFT and he thinks it's false then he will just book a PCR like he has done before.

Flowflex!

So many people getting false positives.

@HalfShrunkMoreToGo

"However, from next week, if he gets a positive LFT while asymptomatic, he is presumed to have Covid and will have to have a week off work. "

No he won't.

The rules will be that you don't have to do a PCR if you get a positive on a LFT but you won't be stopped from getting a PCR. So if he gets a positive on a LFT and he thinks it's false then he will just book a PCR like he has done before.

@HalfShrunkMoreToGo - I'm pretty sure they'll make PCRs far less accessible to asymptomatic people!! We may have to fake symptoms if we want to be able to book.

@ToooutThere even now PCR are for symptomatic unless you have been advised to have one for a particular reason

Oh, wow.

When our headteacher at school announced this change she said that false positives on lateral flows occurred on fewer than 1 in 1000 tests so it would be fine. This is so clearly not the case judging by this thread!!

There's a rumour going round our Year 10s that the children at another school down the road have worked out that if they buy aloe vera drinks from the newsagent next door before taking their test it will be positive. I assumed the rumour was either fake or wrong but maybe not! And, if true, those kids that do this will now buy themselves 7 days off school instead of 1-2!

[quote chopc]@ToooutThere even now PCR are for symptomatic unless you have been advised to have one for a particular reason [/quote]
it may be on paper, but all positive LFDs have to be confirmed by a PCR at the moment.

This does seem to be an issue and I have seen a few cases reported on social media inc MN since the summer when flow flex came in.

However, to those of you saying "oh yeah I had one last month", please note that a positive LFT followed by a negative PCR result is most likely (7-8 times more likely in fact) to be because the PCR result is wrong.

I heard this discussed on our local radio station with a professor of nursing this week, and his advice was to contact your local public health authority and discuss it with them.

To those saying "just get hold of a different brand / the nose and throat sort" - how do you do this unless you know someone with an old stash?

@blameitonthecaffeine i've had numerous conversations with members of school testing teams who say they themselves have tested LFDs with various fizzy drinks and yes they are highly likely to produce a positive result.... kids have long figured this out. If you have half a can of coke before testing, chances are you'll end up with two bars on your test strip.

However, to those of you saying "oh yeah I had one last month", please note that a positive LFT followed by a negative PCR result is most likely (7-8 times more likely in fact) to be because the PCR result is wrong

Each time it happened to dd, we had two PCRs (and in one case three) spread out over a few days. So it was most definitely not the PCRs were wrong.

And the rest of us were fine.