Faint line on LFT after 30mins?

Yeah I know, the result is supposed to be invalid after 30mins, but I never had a line appear after a test even on old tests several days old.

Started feeling like I had a cold this weekend, did a LFT which was negative, did another this morning and a very faint line appeared, but took 40mins plus until I was convinced something was there. A bit clearer now after a few hours but still very faint.

What are the chances I’m positive? Think I read about cross reactivity with other coronaviruses potentially giving false positives on LFT. Have just taken a PCR, so will hopefully find out in the next few days.

Positive
Go get a PCR – don’t pass go

Isolate ASAP

Do another LFT or two for a start.

From personal experience I’d say very likely to be positive but early stages. Best to get a PCR.
Wife and son both had it recently, wife double vacc’ed, son 11 yo. Both v similar – LFD test faint positive in v early stages, confirmed PCR positive, LFD much stronger positive after 1-2 more days then remained positive for another week or so before then testing negative again.

If it was a drugs test in prison it would a positive.
So it’s a positive.

PCR – any line is an indicator of having the lurgy.

We had similar happen here then got a proper positive from another LFT the next day so that’s my guess

If it was a drug test in the Peleton it would mean lots of scrutiny on the B sample

So it’s a court case… 😉

Isolate until PCR comes back.

Mine started at a very faint line. By the next day it was so red the ink was bleeding out!

Hope you feel ok, but I’m with the +ve crew.

I do loads of LFT for work. no matter how long I leave a -ve one there has never been a faint line.

Yep mine was super faint, then the PCR was positive. Says in the bumph, any line no matter how faint should be treated as a positive test and go get PCR.

Makes you wonder how many people don’t even notice a faint positive (or ignore it) and carry on regardless.

One of our daughters got a very faint line (ie, barely visible – so much so I wasn’t sure I could see anything at all) then it went back to nothing for subsequent tests. About two or three weeks later she got a clear positive result and correspondingly positive PCR result – I have no idea if the two were linked.

Now my wife is positive but our other daughter and myself still negative on both LFTs and PCRs.

Positive – Go get a PCR – don’t pass go

PCR – any line is an indicator of having the lurgy.

Not quite so clear cut. It most likely is a very low level of antigen – but lateral flow tests of all sorts can give odd results outside the validated read window.

Now his real dilemma comes when he gets negative on PCR and runs another LF just to be sure – and it is weak positive within the time limit!

Think I read about cross reactivity with other coronaviruses potentially giving false positives on LFT.

mmm… theres also PCR false negatives so I wouldn’t be so quick to assume the LF is wrong. If it is a “false” result its most likely because you read it too late not because of cross reaction with another virus.

but lateral flow tests of all sorts can give odd results outside the validated read window.

Our kits say ignore anything after XX mins (can’t recall what XX is).

Our kits say ignore anything after XX mins (can’t recall what XX is).

Yes, it says ignore after 30mins, but the point being is I never had a line appear on old tests before and I do feel a bit rough

That’ll be bold tomorrow.

That’ll be bold tomorrow.

Was going to suggest the same. My 10 year old was sent home from school as they had lots of cases, LF in the evening had a very feint line. Another LF in the morning had a bold line, PCR was positive.

I’d say assume positive, test again 8 hours or so later and see how that comes back. Or just go an get a PCR.

On symptoms alone then you should isolate.

Yes, it says ignore after 30mins

For the particular kits you have or the last lot [you read the instructions for]? (no offence but who reads instructions every time?)

We’ve now had three types at home, some require reading in a 15-30 window, some not before 30 minutes the others I’ve not had before and haven’t opened yet but, as above, regardless, if there’s a line book a pcr and isolate until you get the result of that. – the worst that can happen is you come back all clear so jabbed your tonsils for no reason.

Also don’t waste time doing another lft, a second is no more accurate than the first so it can’t be used to contradict the previous, you need a pcr for that.

The lft are comparatively inaccurate and significantly less sensitive to actual infection than a PCR (especially in the early stages)

The test is the latest one that you read between 15-30mins.

Well, I’ve just done another one. So far at 15mins it’s completely clear.

45 mins later and the second LFT is completely clear, maybe I’ve already scraped all the covid particles out of my nose on the previous tests🤣

Hopefully will get the PCR result tomorrow

You’ve got symptoms and you’ve done a PCR. Lft kinda irrelevant. Good on you for taking a PCR though.
The amount of symptomatic people I speak to who believe they don’t have covid because they did an lft is frankly staggering. How many of them wait the full 30 minutes is questionable too.
My experience was a very faint line on lft after 20 minutes on the day I spiked a temp (taken after a PCR, whilst waiting for results). Three days later lft was strongly positive in seconds.

I had a faint line too, then subsequent positive pcr, a friend has had exactly the same

The latest nasal only LFT test kits have been shown to be less sensitive than the older nasal and throat tests.

At least within a group of relatives and friends. Some have had negative results on nasal LFT but followed up with a positive PCR test on the same day.

When I had Covid the LFT tests showed negative, that was on days where I felt ill, following a positive PCR test.

If in doubt PCR and isolate until results are back. Then PCR again if negative but symptoms increase.

Son had two faint LFT, an invalid PCR and then negative PCR which was too later to count so isolated anyway. Asymptomatic.

SiL also had faint LFT and then negative PCR next day. Also no symptoms.

Now his real dilemma comes when he gets negative on PCR and runs another LF just to be sure – and it is weak positive within the time limit!

Oh dear, well that has pretty much happened!

Negative PCR back this morning, just did another LFT and there is the very slightest hint of a line at 30mins (when looking closely using phone light)

To be fair I think most people would glance at it and say negative so maybe I am ok.

Mudmuncher, you shouldn’t need a phone light to see if there is a line there or not. But if you can see anything with ordinary lighting it is positive. I suspect there’s a good chance you are asymptomatic with a very low level of infection. The PCR result will have told you you are free to go about life, but I’ve been in similar shoes to you (although my line was not so vague) and I knew I had prolonged contact with a positive case, so I isolated anyway. If you are not inclined to do that I would keep doing daily lateral flow as a minimum.

The latest nasal only LFT test kits have been shown to be less sensitive than the older nasal and throat tests.

Have you got a source for that? Because all the reports I have seen suggest they work better.

Lateral flow tests have pretty much 100% specificity. This means that if they report that you have Covid-19, you have Covid-19.

To be fair I think most people would glance at it and say negative so maybe I am ok.

I wouldn’t. You’re not. Sorry.

Have been taking LFTs 2-3 times a week since February and never seen a line, and I tend to inspect them a bit neurotically.

I would do another lateral flow. make sure you swab your nose thoroughly, and also ensure everything from the swab is transferred into the test fluid. A negative will be no line whatsoever, in any light conditions. The test instructions state that any line, however faint, is a +ve.

As above, Ive done 100s of the damn things.

Treat as +ve get a PCR done. Funnily enough just done the same myself – had booster this morning, have to LFT the night before my 2 days in the office and got a faint line, so our policy is any line is treated as +ve and no access until PCR negative results back.

Good on you for doing the right thing and acting on it.

The latest nasal only LFT test kits have been shown to be less sensitive than the older nasal and throat tests.

Have you got a source for that? Because all the reports I have seen suggest they work better.

I’d hope so, I don’t mind sticking a swab up my nostrils, but the tonsil bit is a major challenge, as in stopping myself from throwing up!
I’ll have to try to track some down – any idea what to look for?

I had a faint line LFT on Christmas Day, redid it again faint line tried for a third time but did it like a pcr throat then nose and it lit up like a traffic light.
Pcr done Boxing Day and positive. Symptoms kicked in Tuesday felt breathless, tachycardia, migraine style headaches,
Wednesday taste and smell went and flu style body aches.
Get a pcr done asap.

I’ll have to try to track some down – any idea what to look for?

Where are you? Flow Flex branded ones supplied if you order online in Scotland are nose only, result in 15 mins. Stocks in other parts of the country may be different.

I’m in Amsterdam at the moment. I didn’t really expect to be here, because when I did my ‘Fit to Fly’ Flowflex LFT, I got a faint red line after the 15 minutes. The company I used didn’t ask you to report a result, just to upload a photo which they would assess and issue a certificate accordingly. So I uploaded a picture of my test, with faint line clearly shown, and while waiting for the result contacted my traveling companions to start revising our plans. While deep in the discussion (this wasn’t about a holiday, a positive test was seriously inconvenient) my email pinged – “your test is negative, here’s your certificate”.

So here I am. I’ve since done 2 more of the NHS nose and throat LFTs both of which have been negative. I have another Flowflex test waiting at home for my Day 2 – be interesting to see what happens with that.

I’m in Amsterdam at the moment. I didn’t really expect to be here, because when I did my ‘Fit to Fly’ Flowflex LFT, I got a faint red line after the 15 minutes. The company I used didn’t ask you to report a result, just to upload a photo which they would assess and issue a certificate accordingly. So I uploaded a picture of my test, with faint line clearly shown, and while waiting for the result contacted my traveling companions to start revising our plans. While deep in the discussion (this wasn’t about a holiday, a positive test was seriously inconvenient) my email pinged – “your test is negative, here’s your certificate”.

So here I am. I’ve since done 2 more of the NHS nose and throat LFTs both of which have been negative. I have another Flowflex test waiting at home for my Day 2 – be interesting to see what happens with that.

Sounds like you were positive – you shouldn’t have got on a plane!

The flow flex tests are more sensitive, when my son had pcr confirmed covid I dropped some of the solution on a flow flex and the older style tests and the flow flex had a more definite line.

Sounds like you were positive – you shouldn’t have got on a plane!

The testing company didn’t think I was positive!

If I was going on a plane I might have been more cautious, but since it was a ferry trip with minimal contact with others I thought I would do what the official process indicated that I should do.

From government rumours, by April we will have stopped testing and isolation anyway…..

The testing company didn’t think I was positive!

If I was going on a plane I might have been more cautious, but since it was a ferry trip with minimal contact with others I thought I would do what the official process indicated that I should do.

I’m going to be blunt. I think you are a selfish idiot. You know deep down the testing company have screwed up you are most likely infectious but not only did you decide to leave the house you got on a ferry to another country. It would be hugely inconvenient – not as inconvenient as the person who directly from you, or indirectly for someone you infect ends up in ITU.

@poly, yes, that was the response I expected on here really, and maybe you’re right. If I thought I was likely to be infected I would have stayed at home. But I don’t go to work, I don’t go anywhere where there are lots of people, where there are people I still socially distance, I still have the Covid app active on my phone, no-one I’ve seen recently had tested positive, I test 3 times a week, I wear a mask. I have no symptoms, and two subsequent tests have been negative. Ultimate caution would suggest I stay at home, but then ultimate caution would have us still in lockdown. I have followed the rules – and that isn’t an ‘I was only following orders’ defence, it was just one of the factors in my decision.

The Flow Flex tests I and family have had are nasal only. Some “NHS” tests supplied by the school The Wife works at are nose and throat.

Like I said, anecdotal evidence, 4 people in the family and two close friends have taken nose only FLT tests which indicated negative results. Followed by either a nose and throat LFT or a PCR which came back positive.

I’m not entirely convinced any of the LFT tests are sensitive enough. When my wife was isolating due to contact with positive cases, her daily LFT tests showed negative, even on the day she felt ill. Three days later an LFT showed positive, confirmed that day with a positive PCR.

I took LFT tests over consecutive days, including the day I did a PCR test, all LFTs were negative, PCR positive. A week later I was still testing negative on LFT tests, even when I was ill in bed.

It could be that I’m crap at taking any Covid test, but if that’s the case why did the PCR test work when others didn’t?