Positive LFTs negative PCR

[ngonizashe]

Hi all

I'm really stressed and at a loss as to what to do.

My 11 year old daughter (home schooled) started feeling slightly more tired than usual Monday afternoon. I did a home Lateral Flow test on her and a faint positive came up. Mine and DH's were negative. We booked a PCR test for all of us the following day. Out of curiosity, the following morning before the PCR test we all retested using Lateral flow tests. Again, a faint positive for DD, negative for the rest of us.
We did the PCR test and waited for results, in the meantime she said she was feeling fine. I did another Lateral flow test on her in the evening, thinking perhaps she was actually at the tail-end of her infection and the line would now be gone. It wasn't - it was neither stronger nor lighter, just the same light positive. The PCR test came in this morning- negative. We did another LFT on her - positive. NHS 119 aren't really helpful - they've just said the PCR takes precedent over the LFT so she is negative.
However if she's had another faint positive since the PCR then it's classes as starting again so she will need to isolate for another 10 days from now or until another PCR comes back negative.

Has anyone heard of this strange situation? All the tests were done by me, not by herself and I ensured she had not had anything to eat or drink in the 30-60 minutes prior.

It is negative. I had this last month. 6 positive LFT, negative PCR. PCR is far more reliable.

LFT are just not reliable. Try one with some coke or fruit juice. You'll get a positive too.

However if she's had another faint positive since the PCR then it's classes as starting again so she will need to isolate for another 10 days from now or until another PCR comes back negative.

Stop testing her for goodness sake. Her PCR is negative. That's all you need to consider.

I think most people know that PCR trumps LFT and false positives are a totally normal limitation of the tests

You're making an issue where none exists unless Im misunderstanding your post.

Yes. This happened to a family member. The false positive rate (if you’re not using acidic drinks) is not very high so I find it odd.

You don’t happen to live in the north east do you op?

False positive rate

The reason I did multiple Tests was because I thought the more I did, the more likely to be accurate. But they all said the same, except 1. PCR negative. No fizzy drinks involved. But felt rough, no covid symptoms.

No idea why.

@everythingthelighttouches

Yes. This happened to a family member. The false positive rate (if you’re not using acidic drinks) is not very high so I find it odd.

You don’t happen to live in the north east do you op?

This might sound stupid but how does a fizzy drink affect a LF? I never knew this so genuinely curious.

Thanks all

No we live in South London, she hadn't had any food or drink beforehand. It's just a strange phenomenon. I suppose I should relax and just be reassured that the PCR is correct and more accurate but I'm stumped as to why these LFTs (these are from 3 different batches too) keep picking up something with her. I guess we may never know!

I think it's much more likely that the PCR test is a false negative. It's more accurate than LFT, but still quite a few false negatives (up to 30%). False positives are rare for both.

I think it's much more likely that the PCR test is a false negative. It's more accurate than LFT, but still quite a few false negatives (up to 30%). False positives are rare for both

This is a good point.

I would get another pcr and stop using the lateral flow. Could possibly be a false negative especially after so many positive lfts. Strange

What was the outcome OP?
I've had several positive lateral flows today and awaiting PCR result

Negative on PCR. Never did get to the bottom of it. She’s negative now on LFTs.

@everythingthelighttouches

Yes. This happened to a family member. The false positive rate (if you’re not using acidic drinks) is not very high so I find it odd.

You don’t happen to live in the north east do you op?

I know this is from a few weeks ago, but what's the relevance of the north east? I ask because DD and I have both had several very faint but positive LFTs this week, but both our PCRs were negative. When we tested yesterday from a new box of LFTs we were negative, too. Is there a dodgy batch up here or something?