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Original poster

Lateral flow tests...

67 replies

sopositivelynegative · 27/07/2021 15:40

Checked my LFT at exactly 30 minutes and at first glance there isn't a line, but if I hold it up to the light, there's a very pale shadow at the positive bit. So pale and you have to squint.

(Is there supposed to be a shadow? Like, a sort of place marker for where it would turn purple if did change colour?)

My LFTs all look negative, but after 30 minutes, they do turn positive. I know results after 30 minutes are supposed to be void, but everyone I've spoken to has said that theirs are always negative and stay negative.

Anyone had similar/understand the science of how these tests work?

OP posts:
Thread gallery
5
Tippexy · 01/08/2021 10:04

@Mummybasketball, @snapple21’s first photo is certainly positive. The LFTs are like pregnancy tests, you don’t always get a really strong line but it’s still positive.

snapple21 · 01/08/2021 14:04

It clearly is positive Hmm albeit faint.

YarnOver · 01/08/2021 14:05

@sopositivelynegative

Have tried to attach a photo to this... Warning, it's even less clear on the screen. You'll have to really squint.

It's nothing like @whenimwrongiknowimwrong's very definite test!

No need to squint that's a very obvious positive line.
Original poster
sopositivelynegative · 01/08/2021 15:17

@YarnOver I think I probably confused matters for some posters.

Let me recap...

  1. I took a LFT test that had a faint positive line at 30 minutes, visible only to the eye. My phone camera is terrible and couldn't pick it up to share with you all.

  2. The line got darker after 30 minutes, and the photo I took was after 30 minutes, but how it looked in the photo reflected how it looked in real life at 30 minutes to the eye.

  3. Separately, all of my LFTs turn positive after 30 minutes, even when they are completely negative at 30 minutes. I thought that was an odd phenomenon and wondered if any posters had had similar experiences. Some had, some hadn't.

  4. After the faint positive LFT test, I took a second one (from a different pack) that was completely negative at 30 minutes, so I wonder if it was just a dodgy set of seven.

  5. A PCR test confirmed the second LFT negative was in fact correct.

PS Point 3) still baffles me! If a negative test turns positive after 30 minutes, I count it as a negative, but I think it's odd, and if anyone understands the science, I'd love an explanation!

OP posts:
ThorIsAGod · 01/08/2021 15:35

@sopositivelynegative do you think it was a dodgy batch? I don't know of anyone else who has this phenomenon. Most people I know do them, leave them kicking about and go and have a look at some time later. I don't think anywhere in the instructions does it say that you must look at exactly 30 mins or that it'll go positive after, does it?

User5827372728 · 01/08/2021 15:38

I’ve just done a pcr test for a very faint line on a LFT to! Not sure what time the line appeared!

Glad your PCR was negative, praying mine is too

Darbs76 · 01/08/2021 15:57

Mine were so faint at first. But I was positive

YarnOver · 01/08/2021 19:05

[quote sopositivelynegative]@YarnOver I think I probably confused matters for some posters.

Let me recap...

  1. I took a LFT test that had a faint positive line at 30 minutes, visible only to the eye. My phone camera is terrible and couldn't pick it up to share with you all.

  2. The line got darker after 30 minutes, and the photo I took was after 30 minutes, but how it looked in the photo reflected how it looked in real life at 30 minutes to the eye.

  3. Separately, all of my LFTs turn positive after 30 minutes, even when they are completely negative at 30 minutes. I thought that was an odd phenomenon and wondered if any posters had had similar experiences. Some had, some hadn't.

  4. After the faint positive LFT test, I took a second one (from a different pack) that was completely negative at 30 minutes, so I wonder if it was just a dodgy set of seven.

  5. A PCR test confirmed the second LFT negative was in fact correct.

PS Point 3) still baffles me! If a negative test turns positive after 30 minutes, I count it as a negative, but I think it's odd, and if anyone understands the science, I'd love an explanation![/quote]
Ok

FuckingFabulous · 02/08/2021 19:34

I've had about a dozen positive lateral flows and no positive PCR

ThankyouForListening · 03/08/2021 06:21

That’s so odd- are you unwell too?

milkysmum · 03/08/2021 06:57

The test results overall can be so inconsistent it's infuriating. I work in social care so test regularly.
I tested positive on a routine PCR back in January, but the LFT showed negative. I developed symptoms a day or two later, I did another LFT, still me negative, I did another PCR- negative? I clearly had tested positive and was by this point very symptomatic. We had a significant outbreak in the workplace. I need an antibody test the month later that said I hadn't had covid- so confused!?

Watapalava · 03/08/2021 07:22

I honestly despair at all these people testing themselves whilst perfectly healthy

Your ‘contact’ are going to love you - do people realise no one wants to be forced into isolation in August - give it a rest everyone who’s vulnerable is vaccinated

AbsolutelyPatsy · 03/08/2021 08:46

yup, the instructions are to look at 30 minutes,
do not leave it as it might change
i knew this,
are people not reading the instructions?

NotMyCat · 03/08/2021 08:51

@Watapalava no, not everyone vulnerable is vaccinated. And some are vaccinated with no antibodies. And CEV children
People are testing so they don't pass it on to say someone with blood cancer who hasn't made any antibodies

User5827372728 · 03/08/2021 08:53

My PCR was negative after a positive LFT.

@Watapalava

That’s a terrible attitude.

ThorIsAGod · 18/08/2021 22:28

@AbsolutelyPatsy

yup, the instructions are to look at 30 minutes, do not leave it as it might change i knew this, are people not reading the instructions?
@AbsolutelyPatsy I realise it's taken me a while to come back to this but I've read through the instructions again today and remembered what you said. No where does it say you must look at 30 mins, it just says look after 30 mins as it could still change after 20.
LRSD · 27/08/2021 19:34

Just wanted to chime in here (I posted this exact message on a similar thread) - I’ve just had this exact same thing. Did an LFT before work, negative, returned 10 hours later to clear my desk and saw two very clear lines. Cue panic. Did 3 x more LFTs there and then (all three different brands lol) and all negative. Still wasn’t convinced as had been found my friend who then tested positive and have CEV partner. Booked a PCR for that night. Whilst waiting for results I rooted through the bins for all the ones of that brand and they ALL bar one had 2 lines and they’d all been negative at 30 mins.

Got my PCR result today negative. The gov advice and NHS site advice say if you’ve left it longer than 30 mins do not log it as positive and conduct the test again. The people at the PCR test centre all also said it was a void LFT and not to worry. Just wanting to put people’s minds at ease smile

Also, the brand this happened was the Orient Gene ones which has been mentioned to do this before. X

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