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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
BlackInk · 27/07/2021 15:43

We've done dozens of LFTs and never seen the slightest hint of a 2nd line on them. Official advice is that any line read at the correct time is a positive.

PCR tests are easy to come by at the moment. I would get one just to be sure.

Can you post a pic of your test?

whenimwrongiknowimwrong · 27/07/2021 15:46

This is my one from this morning, 2 very clear lines came up within minutes

Lateral flow tests...
sd249 · 27/07/2021 15:49

A line - even a very faint one is a positive. I've done thousands of tests as I worked in a test centre and never seen one go positive after 30 minutes if it was initially negative.

I'm sure it can- but I've never seen it and because of my role I always saw the tests after the 30 minutes!

Original poster
sopositivelynegative · 27/07/2021 15:58

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!

Lateral flow tests...
OP posts:
QueenStromba · 27/07/2021 16:00

That's positive, sorry.

MereDintofPandiculation · 27/07/2021 16:03

That's positive, sorry. Only if it came up in the first 30mins. If it appeared after 30mins, it's not.

SunbathingDragon · 27/07/2021 16:04

If it wasn’t there at 30 mins, then it’s negative. I’ve had loads of LFT with a slight second line come up a long time after the 30 min cut off and in the early days I would have a PCR afterwards (always negative). I’ve also had loads more LFT stay totally negative afterwards.

Cookerhood · 27/07/2021 16:05

I know someone who left their lying around for a couple of hours & there was a very faint line. I would have thrown it away but she got a PCR which was positive. Over the next few days all LFTs negative. Go figure.

Original poster
sopositivelynegative · 27/07/2021 16:06

Interesting you've had the same experience, @SunbathingDragon

It wasn't as dark as at that at 30 minutes, but there was a very, very faint line in that place. I had to really stare at it, but there was something there.

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PeonyTime · 27/07/2021 16:06

That's positive, OP.
There is absolutly no hint of anything on the negatives. I've seen about eleventy million of the things at work.

PeonyTime · 27/07/2021 16:08

Oh, hang on. That's not at 30 mins???? I'd take another one, being really through with the swabbing.

Atypicaldancer · 27/07/2021 16:08

Mine never came up positive until after I got my positive PCR so I would say that was positive.

Original poster
sopositivelynegative · 27/07/2021 16:10

Right, I've got a couple of LFTs left in this pack, but I'm going to break out a new pack just in case this one is rubbish. Will do that first.

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SPSN · 27/07/2021 16:20

My husband's test looked like this. He didn't even notice the line it was so faint but I could see it. He went for a PCR a few hours later and it was positive.

RapidRollerSkater · 27/07/2021 16:23

You need to do a PCR.

DoubleDeckerSwimmer · 27/07/2021 16:27

My child's line looked like that and his PCR was positive.

ruumis · 27/07/2021 16:32

I had negative lft and there was no line even after thirty mins. Pcr was negative too. Test of the family had a line of some sort and positive pcr.

Original poster
sopositivelynegative · 27/07/2021 16:48

@PeonyTime

Oh, hang on. That's not at 30 mins???? I'd take another one, being really through with the swabbing.
Second one (from a different pack of 7) looks completely negative at 30 minutes. And I'm staring it really carefully to look for a line!

I wonder if it was just a dud kit?

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lookingsusbro · 27/07/2021 16:59

That's how mine and ds2's looked and we both had positive pcr tests a few hours later.

On the flip side ds1 had a negative lft test and his pcr the following day was positive. I'd say you need to book a pcr test op.

Lemons1571 · 27/07/2021 17:08

@DoubleDeckerSwimmer

My child's line looked like that and his PCR was positive.
Same here for both my children. PCR confirmed positives.
Lemons1571 · 27/07/2021 17:09

@sopositivelynegative can you post a pic of test 2?

TuesdayRuby · 27/07/2021 17:11

Looks positive to me. All the LFT that I’ve done have been negative, and they’ve never had a line, even past 30min

jumpbounce · 27/07/2021 17:13

I've had 2 of those the same OP very faint lines, currently awaiting PCR results.

Muchtoomuchtodo · 27/07/2021 17:16

Blimey. I’ve always assumed that a line on a positive test would be really obvious.
I never squint to see if I can make a second line out!
So if that was my test it would have been reported as a negative and I’d have carried on as normal.

Original poster
sopositivelynegative · 27/07/2021 20:39

[quote Lemons1571]@sopositivelynegative can you post a pic of test 2?[/quote]
The second one was completely clear at 30 minutes - no line at all.

(It did develop a faint line after 30 minutes though... Fainter than the last one.)

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