Lft negative, pcr positive. No symptoms

[Girlmama3]

Two secondary school children here have tested positive pcr, still negative lft and no symptoms.

Has anyone else had this? I thought lfts picked it up without symptoms and pcr with? Makes me wonder why I’m using lft on my children 🙄

LFTs are a complete waste of time, you might as well toss a coin because the result will be about as accurate.

They might be asymptomatic, or the PCR might be picking up on a covid infection within the last 90 days that's no longer infectious (you're not meant to repeat PCR tests within 90 days of a confirmed infection for this reason).

Lfts only pick up 40% - 50% of positive cases where covid is present, regardless of symptoms. It's an order or two of magnitude more likely to be a false negative lft than a false positive pcr.

They probably have a low viral load (because they're young), so the LFT isn't picking it up. PCRs are much more sensitive, which is why they should be used for people with symptoms - you are much more likely to have Covid if you have symptoms!

LFTs are just for picking up asymptomatic cases.

It's got nothing to do with lfts picking up asymptomatic, and pcrs picking up symptomatic. They're the same test but one done at home with margin of error and one done in the lab. Lfts are notoriously unreliable. Why did you get them a PCR if no symptoms and neg Lft?

If they have had a positive PCR they have it. LFTs will pick up about 50% of cases - so they're kind of a useful check if you have no symptoms but they don't pick up every case. It's not "PCR tests for symptomatic cases and LFT tests for non-symptomatic". It's "PCR tests are reliable for any cases but expensive and slow, LFTs are unreliable but quick and cheap so handy to do regularly to pick up some of the cases we'd otherwise miss completely". If they've tested positive with a PCR they have it.

@HalloHello

It's got nothing to do with lfts picking up asymptomatic, and pcrs picking up symptomatic. They're the same test but one done at home with margin of error and one done in the lab. Lfts are notoriously unreliable. Why did you get them a PCR if no symptoms and neg Lft?

They arent the same test as they look for different things. LFTs are not very reliable unless you have a high viral load and are very good at taking a sample

Pcrs are being used if you’ve had close contact now as well as if you have symptoms.

I think the two children had very close contact with the positive child hence the tests.

What a waste of time. I’ve been using lfts on my children this week as their isolating. Thanks all.

LFTs are there to do a wide sweep to pick up a load of asymptomatic cases we’d otherwise not know about. Half of them get missed anyway cos LFTs are a bit shit.

A negative LFT means “the test didn’t find covid”. It doesn’t mean “you don’t have covid”.

LFTs are basically a waste of money and plastic

They're asking people to use LFTs regularly because picking up a proportion of asymptomatic cases is better than picking up none and at a population level makes a difference to cases.

On an individual level they're not particularly reliable in saying you've definitely not got covid. A pcr test should be more reliable and a positive PCR 'trumps' a negative LFT.

New research is showing that LFTs are actually pretty reliable when symptoms first develop but that's not how we are using them atm.

A friend of mine had a positive PCR and continued to do daily lateral flows. It was only by day 3 the lateral flows picked up the virus.

www.qmul.ac.uk/media/news/2021/smd/lateral-flow-tests-are-95-effective-at-detecting-covid-19-when-used-at-the-onset-of-symptoms.html
Lateral flow tests are 95% accurate when used at the onset of new symptoms

The LFTs were junk tests and the government had to do something with them, so give them out to all and sundry.

They state it’s for those without symptoms - basically a “better than nothing”. But if you do have symptoms then yes they could pick up the virus in some cases. But the accuracy rate is woeful.

@HalloHello

It's got nothing to do with lfts picking up asymptomatic, and pcrs picking up symptomatic. They're the same test but one done at home with margin of error and one done in the lab. Lfts are notoriously unreliable. Why did you get them a PCR if no symptoms and neg Lft?

They are the same sampling method, but absolutely not the same test.

Same here, positive PCR but negative LFT's last week and all this week, including after symptoms started. Full on cough and sore throat today and still negative.

Friend (in healthcare, double jabbed) with Delta symptoms had to do 3 LF to get even a faint +ve; PCR positive. I had -ve LF the days before and after my +ve pcr. pharmaceutical-journal.com/article/feature/how-reliable-are-lateral-flow-covid-19-tests