Two negatives after positive lateral flow

[Neolara]

I took a LF at lunch time, I think before eating, and them promptly forgot about it. My DH found it about 1.5 hours later and there was a clear second line. I was so surprised, I took another LF to double check. This didn't have a hint of a positive at 30 mins or now, hours later. So then I took another LF and that was similarly negative.

I've booked a PCR for tomorrow, but make my day and reassure me the first LF is likely to be a false negative. I don't want to spend Xmas in isolation.

You arent supposed to check after the stated time. It could be an evaporation line.

If it went past the 30 minutes then ignore it. Very likely you are negative

Sorry but I disagree. If there was a strong second line it won't be an evaporation line.

We've had this with a strong positive LFT and then repeated it and it was negative. PCR was positive. I wondered if the first LFT had somehow collected all the virus so there wasn't enough left for the second LFT to be accurate?

In any case, lots of people test positive on PCR but negative on LFT. I'm afraid it's just a waiting game now...

@Moolia

Sorry but I disagree. If there was a strong second line it won't be an evaporation line.

We've had this with a strong positive LFT and then repeated it and it was negative. PCR was positive. I wondered if the first LFT had somehow collected all the virus so there wasn't enough left for the second LFT to be accurate?

In any case, lots of people test positive on PCR but negative on LFT. I'm afraid it's just a waiting game now...

But it was left for more than an hour after it was supposed to be checked. Results after the time limit are not valid

Where the two you took afterwards a different brand than the first? My partner had multiple positives on the blue brand but testing negative on the green and white brand

If you have it then it would show up on all 3 tests. You can’t swab the virus “out of your nose” with one test and none left. Bit of waste time doing a PCR if you have no symptoms and did the test wrong

Definitely not a waste of time doing a PCR. Really hope it's negative!

Was it an orientgene? We've been getting evaporation lines on those when we don't on 3 other brands. (we have multiple boxes in the house as OH brings home from work). All tests negative at 15/30 mins but almost all the orientgene get an evap line when OH does them, the others don't. He's also negative on multiple pcrs and no symptoms so in this instance I think the negative at 15 mins is correct.
I would still do another LF in the morning and a PCR to check.

"I wondered if the first LFT had somehow collected all the virus so there wasn't enough left for the second LFT to be accurate? "

Sorry but this made me LOL

Thanks all for your thoughts. I can't actually remember if the tests came from different boxes. I think they were all dark blue brands, definitely not the green ones. My DS has covid at the moment and is isolating at home which makes a positive result more likely unfortunately. I guess only a PCR will confirm.

Update. My PCR came back negative. Phew. I'll be putting my LFs in the bin after the cut off point from now on.