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Original poster

Settle a LF test argument between me and DH please.

24 replies

tumpletops · 14/12/2021 00:03

He thinks that if the test is positive, the line will show immediately as the liquid moves up the gauge. So it's it clear at the start, it will stay clear. It may start off very feint, but if it's positive some kind of line will be visible straight away.

I don't necessarily agree, and think it could start off completely blank but then develop within the 15mins / 30mins that you are supposed to wait.

We have no experience (so far) of a positive LFT in our house.

Who's right??

OP posts:
gsaoej · 14/12/2021 00:04

He’s wrong. DD’s positive took 25 mins to show up even faintly.

gsaoej · 14/12/2021 00:04

Confirmed by PCR

tldr · 14/12/2021 00:06

You’re right. 15 or 30. Read the instructions.

CheesyFootballsAreEvil · 14/12/2021 00:08

He's wrong and needs to read the instructions again

Peanutmnm · 14/12/2021 00:09

He's right about all the positive LFTs in our house. Positive as the fluid crept up. Clear as day.

Plexie · 14/12/2021 00:10

Is there a reason your husband is unable to read the instructions? It quite clearly states you need to wait 15-30 minutes.

NeedAHoliday2021 · 14/12/2021 00:11

Our positives have been really strong and instantly obvious, within seconds, but that’s not the case for everyone.

snowdropsandcrocuses · 14/12/2021 00:12

All positives in our house immediately visible. Never had a test yet that developed a positive later

Original poster
tumpletops · 14/12/2021 00:12

@CheesyFootballsAreEvil

He's wrong and needs to read the instructions again
It's not that he hasn't read the instructions, and does check after the allotted waiting time. He just thinks that with the way the chemicals work, you'd get an immediate even if very feint line. It's interesting to hear that's not the case.
OP posts:
snowdropsandcrocuses · 14/12/2021 00:12

@Plexie

Is there a reason your husband is unable to read the instructions? It quite clearly states you need to wait 15-30 minutes.
Not sure why you have to be rude!
Original poster
tumpletops · 14/12/2021 00:13

@Plexie

Is there a reason your husband is unable to read the instructions? It quite clearly states you need to wait 15-30 minutes.
He's perfectly capable of reading the instructions...
OP posts:
TurquoiseBaubles · 14/12/2021 00:13

No. A seemingly instant negative, followed by a very faint line after 20 minutes has led to a full instant line the following morning on two occasions in this house.

TurquoiseBaubles · 14/12/2021 00:16

In our cases they appeared absolutely clear after two minutes, but had he faintest shadow after 20. The following morning's LFTs were, in both cases, strong positives.

I've taken this as a great way of getting a 24 hour warning of being infectious, with the assumption that the "almost negative" means "not infectious yet" and the next day being "fucking hell I need to isolate" Grin

greenlynx · 14/12/2021 00:16

You need to leave it for 30 minutes in a flat surface at normal temperature and only then to check.

Plexie · 14/12/2021 00:17

Not sure why you have to be rude!

I wasn't being rude, I was allowing for the possibility he is illiterate or can't read English.

greenlynx · 14/12/2021 00:17

Sorry on a flat surface not in

Original poster
tumpletops · 14/12/2021 00:20

Ok maybe I should have made it clearer in my OP. It's not that DH can't read / doesn't understand the instructions. He thinks from a science POV as soon as a positive sample moves up past the test line it will show, even if just slightly. I wasn't sure. Hope that clears it up!

OP posts:
TurquoiseBaubles · 14/12/2021 00:24

Well he's wrong. If there is a low dose of virus present in the sample, it can take up to 30 minutes to show up on the test. That's why the instructions say to wait before reading.

Sonex · 14/12/2021 00:29

This seems counter intuitive to me. If the chemiclamon the test is reacting to a viral antigen I don't understand why it would take time to complete whatever chemical colour change happens. like pregnancy tests don't take 20 mins to show the line, I assumed they worked in the same way.

does it take longer if there's very little virus in the sample or something? I don't doubt any of you (never had a positive here), I just don't understand scientifically what's behind it.

Plexie · 14/12/2021 00:30

As a result of this thread I'll now check my tests after 2 minutes, 20 minutes and 30 minutes!

Bumpsadaisie · 14/12/2021 00:32

I watched mine for 10 mins - the rest of the house was positive so I was testing daily. Mine totally clear and I though oh sod it still haven't got it, I wish I would get on and catch it!

Went back at 30 mins - and a faint line. Confirmed by PCR.

TurquoiseBaubles · 14/12/2021 00:34

The comparison to pregnancy tests is that a very faint (pretty much invisible) line is positive, and is usually followed by a stronger line if repeated the next day.

The (very faint) positive after 20 minutes indicates a (very low) presence of virus. If the person is beginning a covid infection it will be stronger the next day. LFTs of people recovering from covid usually show a fainter and fainter (and longer to appear) line over time.

Adelerous · 14/12/2021 00:43

The two positives we’ve had both looked negative for the first ten minutes!

AlexaShutUp · 14/12/2021 00:44

He's wrong. DD's line didn't show up for around 20 mins, and even then it was very, very faint. It was later confirmed by a pcr test. I have heard that some people get much stronger lines that show up very quickly. Maybe it depends on the viral load? Confused

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