How many of you are getting negative LFT but positive PCR with omicron?

[Lovemusic33]

Have LFT all 3 of us this morning, dd2 has cold symptoms (sneezing mainly, runny nose), all of us testing negative. Dd1 tells me that the nasal swab LFT are not picking up omicron?

Dd2 booked for PCR this morning as she can not go back to school until she has one due to her having a runny nose.

When we had delta in September my LFT was negative but PCR positive when I had no symptoms but dd1’s was positive with symptoms.

How many of you are getting negative LFT but are then getting a positive PCC with possible omicron?

What’s the chances of dd2 being negative in the PCR and her just having a cold?

DF had negative LFT but positive PCR which he took as a close contact of a positive case (still required in Scotland). No symptoms at all. My DH is also a close contact (of me!) but tested consistently negative on LFT. this clearly doesn’t mean he hasn’t had covid but he has followed the guidance……

Thank you for your replies, it’s really interesting that some are getting negative LFT with and without symptoms but getting positive PCR.

We have just been to get a PCR so will now wait and see. Dd is sneezing a lot, occasionally coughing but mainly just a snotty nose. Keeping everything crossed that she’s negative, mainly because I can’t cope with her home for another week 😬. Dd1 went back to school today, took a LFT before leaving the house and will be taking one at school.

It just makes me wonder how accurate tests are and how many people are out there working/going to school believing they are negative when infact they have covid.

Same here. My son has Covid (day 6) and all my daily LFTs have been negative. Sore throat since Saturday and generally feeling a bit poorly so booked PCR. PCR on Saturday, Sunday and even this morning still negative but PCR result came through just now as positive.

Don't rely on LFT if you have any symptoms at all - book PCR.

@DesdemonaDryEyes it was my stepson, not me. He had been away at an event and required to test daily. Was negative Thurs, Fri, Sat, Sun. Monday he felt odd and had a very strong positive lft. Did another to confirm and also immediate strong positive. His first pcr took 3 days to come back as "inconclusive" so we booked another. This came back as negative but he still had really strong positive lft so we booked another one before sending him out mingling with elderly family members. It came back positive.

We ignored the initial pcr results as it seemed likely they were incorrect and didn't want to put others at risk.

@Gemma77

Same here. My son has Covid (day 6) and all my daily LFTs have been negative. Sore throat since Saturday and generally feeling a bit poorly so booked PCR. PCR on Saturday, Sunday and even this morning still negative but PCR result came through just now as positive.

Don't rely on LFT if you have any symptoms at all - book PCR.

Sorry should say LFT on Saturday Sunday and Monday negative- PCR positive

Samw as you op. Majority of our household has come down with a flu like cold that just wont budge. All of us doing ltfs coming back negative. About to go do a pcr now. Everyone has been sick for over a week now with all the classic omricon symptons so it either is a super cold or ltfs are useless.

@ChequerBoard
LFTs need a higher amount of virus present to give a positive than PCRs ie PCRs are more sensitive. People with symptoms often, but not always have a higher amount of virus present in the nose and throat than those without, so yes, they absolutely do detect positives in people with symptoms too.
The reason PCRs are just recommended for people with symptoms/ close contacts is to target finite resources and prioritise testing those most likely to be infected.
LFTs detect only around 53% of positive cases. Testing the population regularly, regardless of symptoms will therefore identify 53% of cases, which (assuming they then isolate) stops those 53% infecting others.
PCRs detect 98% (or higher, depending which study you read). If more PCRs were available, and the population could be tested regularly using those instead (without slowing the processing time to the point that results were meaningless) then that would remove 98% of cases from circulation. But this can’t happen with current resources.
In order to target testing most effectively, the guidance is LFT for everyone, PCR for those with symptoms/ close contacts.
Neither can tell if you have symptoms, and neither works better or worse depending on whether or not you are symptomatic.
Most people are close to zero infectiousness by day 6. The day 6/7 LFTs are to detect those outliers who may still be infectious by identifying those who still have high amounts of viral material detectable. A PCR couldn’t be used for this because, as it’s so much more sensitive, it would give a positive due to “dead” viral fragments.

[quote Howmanysleepsnow]@ChequerBoard
LFTs need a higher amount of virus present to give a positive than PCRs ie PCRs are more sensitive. People with symptoms often, but not always have a higher amount of virus present in the nose and throat than those without, so yes, they absolutely do detect positives in people with symptoms too.
The reason PCRs are just recommended for people with symptoms/ close contacts is to target finite resources and prioritise testing those most likely to be infected.
LFTs detect only around 53% of positive cases. Testing the population regularly, regardless of symptoms will therefore identify 53% of cases, which (assuming they then isolate) stops those 53% infecting others.
PCRs detect 98% (or higher, depending which study you read). If more PCRs were available, and the population could be tested regularly using those instead (without slowing the processing time to the point that results were meaningless) then that would remove 98% of cases from circulation. But this can’t happen with current resources.
In order to target testing most effectively, the guidance is LFT for everyone, PCR for those with symptoms/ close contacts.
Neither can tell if you have symptoms, and neither works better or worse depending on whether or not you are symptomatic.
Most people are close to zero infectiousness by day 6. The day 6/7 LFTs are to detect those outliers who may still be infectious by identifying those who still have high amounts of viral material detectable. A PCR couldn’t be used for this because, as it’s so much more sensitive, it would give a positive due to “dead” viral fragments.[/quote]

Yes thanks I know all that.

My point was that LFTs are a not just for use when. There are no symptoms present.

Many posters continue to say that LFTs 'don't work when there are symptoms' this is not correct and is not the reason for follow up PCR testing as was claimed.

My lateral flow tests were all negative until after a positive PCR despite having obvious symptoms by then. DP had a few negative lateral flow tests, then a positive which prompted both of us to book the PCR. I don't think we had Omicron because both of us have affected taste and smell, still not 100% three weeks later.

@Iseeyoulookingatme

Lfts aren't as accurate as pcr tests, they are there for picking up asymptomatic cases. That's why if you have symptoms you have to book a pcr test.

No, I know you are using colloquial language but it's important to use the correct phrase. LFTs are not as sensitive as PCRs. PCR tests will pick up some cases that LFTs do not (including false positives post infection). Both tests have the issue of user error, people don't like putting thing down their throat or up their nose and that has the biggest impact on the results.

LFTs are cheap, quick, and easy to use and despite everything you see on here actually very good at picking up asymptomatic infection. They also will give a positive result for symptomatic cases but for various reasons the government stats are based on the PCR results and so we all have to do a PCR if symptomatic and/or if we have a positive LFT.

I'm not sure which version we had last month but DS had a cough, positive LFT straight away followed by positive PCR. Initially I had negative LFT but positive PCR, within a few days my LFT became positive and I had a blocked nose and headache.
DD had no symptoms and negative LFTs all the way through but positive PCR on day 10 of my isolation! I only got her (and OH who stayed negative) retested to be extra cautious before reopening my childcare setting!

I know of 4 ppl who were negative with lft but positive pcr. The worrying thing is that some folk rely on these lft to visit elderly relatives etc. We had bad colds last week so got pcr tests even though lateral flows were negative. I just don't trust them.

@endlesscraziness Do you have a link to the SAGE papers about LFTs please?? I'd like to find out about this. I have COVID just now and going stir crazy in isolation. I don't have enough LFTs to test every day due to the shortage and I'm in Scotland so have to isolate for 10 days anyway. I'm going to do an LFT on the very beginning of day 11, if it's positive I want to know if I'll still be infectious. Basically, if LFT is positive does that = a chance of still being infectious, or can it pick up 'old' covid??

[quote slugsandsnailsandchippednails]@endlesscraziness Do you have a link to the SAGE papers about LFTs please?? I'd like to find out about this. I have COVID just now and going stir crazy in isolation. I don't have enough LFTs to test every day due to the shortage and I'm in Scotland so have to isolate for 10 days anyway. I'm going to do an LFT on the very beginning of day 11, if it's positive I want to know if I'll still be infectious. Basically, if LFT is positive does that = a chance of still being infectious, or can it pick up 'old' covid??[/quote]
You dont need a negative LFT to leave isolation. Once you have done your 10 days you are free to leave isolation even if the LFT shows positive after that

You dont need a negative LFT to leave isolation. Once you have done your 10 days you are free to leave isolation even if the LFT shows positive after that

You can leave isolation after 10 full days (not including the first day of symptoms or day of test if asymptomatic). However that wasn't the question; I too am interested to know if a positive LFT indicates continuing infectiousness.

Have skin in the game as stupid BIL came to a family dinner on Sunday which was Day 10 of his isolation period and he got a stonkingly strong positive LFT result that morning! I really hope he wasn't infectious, but it seems incredibly unlikely given he was getting such a strong positive LFT (test line clearly and strongly appearing even before the control line had showed up, which was what my own LFTs did at the height of my infection in October).

From what I've read it seems you are unlikely to be infectious after 10 days although I imagine there will be some outliers who shed for longer.

All.the .gov site says is;

You should not take any moreLFDtests after the 10th day of your isolation period and you may stop self-isolating after this day. This is because you are unlikely to be infectious after the 10th day of your isolation period. Even if you have a positiveLFDtest result on the 10th day of your self-isolation period you should not take any moreLFDtests after this day. If you are concerned you may choose to keep following the above advice until 14 days after the start of your self-isolation period.

@slugsandsnailsandchippednails this is a contentious subject around infection control leads! You're more likely to have a lasting PCR than an LFT, but previous advice stated you shouldn't do either for 90 days post positive, then in the healthcare worker guidance it said to test lft until clear

I'll find them for you

https://www.independentsage.org/wp-content/uploads/2020/09/Indie-SAGE-testing-document-Final-110920-12.05.pdf

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachmentdata/file/943187/S09255InnovaLaterallFlowSARS-CoV-22Antigentesttaccuracy.pdf

www.bmj.com/content/372/bmj.n208

I’m in the middle of self-isolation after a positive pcr (close contact). I’ve done a ltf every day since and they are still resolutely negative. I’m asymptomatic so I guess my viral load isn’t enough to show up?

[quote endlesscraziness]@slugsandsnailsandchippednails this is a contentious subject around infection control leads! You're more likely to have a lasting PCR than an LFT, but previous advice stated you shouldn't do either for 90 days post positive, then in the healthcare worker guidance it said to test lft until clear

I'll find them for you [/quote]
that's intersting.
Yes our work guidance (NHS) was previously not to retest lft or pcr for 90 days, new guidance out a couple of weeks ago now states we need 2 negative lateral flow tests (from day 6 onwards) before we can return, even if that takes us past 10 days......I was panicking when my day 6 lft was still positive last week, but thankfully days 7 and 8 were negative so I could go back today (which was day 11 anyway)

@Kerzel

I’m in the middle of self-isolation after a positive pcr (close contact). I’ve done a ltf every day since and they are still resolutely negative. I’m asymptomatic so I guess my viral load isn’t enough to show up?

Or you’ve already had it and the PCR is still picking this up.

My nasal swab picked up omicron first go

All of my LFT have been negative, I felt terrible and very symptomatic so went for a PCR- positive. This is the second time I have had covid, the first time it was picked up straight away by LFT and PCR. This time has been much worse, probably due to the fact I am on immunosuppressants.

@dementedpixie

From what I've read it seems you are unlikely to be infectious after 10 days although I imagine there will be some outliers who shed for longer.

Yes there are - the original isolation period was 14 days. Then it was reduced to 10 as most cases stop being infection after then. Some may be infectious for more than 14 days but it’s a minority.