Positive LFT, negative PCR, coughing and painful chest.

[LadyFlumpalot]

Hi all, looking for some advice here.

I tested positive on an LFT on Thursday morning. I took the test as due to see in-laws. Obviously I booked a PCR as soon as I could which happened yesterday and I had a negative result this morning.

However, since I took the LFT I've started coughing and have a painful chest. I do not have a temp and can still taste and smell absolutely normally. I do have form for winter coughs and after a nasty dose of Bronchitis in 2018 my lungs are sensitive and ache as standard with a cough.

I'm due my booster tomorrow, can I still get it as I have had a negative PCR? Cannot get through to anyone at 119 to ask.

My gut reaction is that I do not have COVID and had a false positive, however I don't know if I'm supposed to go get another PCR as I'm still coughing, Google just says to trust the PCR result over the LFT.

For clarity, I started coughing before the PCR but after the LFT. LFT positive, PCR negative.

Help!

False positive LFTs are really, really rare. False negative PCRs happen up to about a third of the time, so very common.

Take another LFT and if positive again then assume you have Covid.

Please don't go for your booster until you've had another PCR.

@Haffiana

False positive LFTs are really, really rare. False negative PCRs happen up to about a third of the time, so very common.

Take another LFT and if positive again then assume you have Covid.

Ok, LFT just now is negative. So is that it then? I trust the PCR and the new negative LFT and assume the first was an anomaly?

@Lacedwithgrace

Please don't go for your booster until you've had another PCR.

No PCRs available in my area and as my booster is tomorrow I can't wait for a postal one and result. Just don't another LFT and it's negative. I am going to take that and my negative PCR as the answer.

I'm also going to attempt to find a grip and stop flustering quite so damn much.

False negative PCR up to a third? Surely that's not right? Pretty pointless if that's the case.

@Haffiana

False positive LFTs are really, really rare. False negative PCRs happen up to about a third of the time, so very common.

Take another LFT and if positive again then assume you have Covid.

Sorry but they are really, really not. I have had several followed by negative PCRs since August.

There have been several threads on this.

Not an excuse for not going for a PCR though.

How are you actually feeling OP? If you are ill with anything, I would postpone the booster a few days.

For both your sake and the people you will meet at the vaccine centre - wouldn't be nice to pass on anything to them, even if it isn't covid.

I had my booster whilst I had a cold (negative lft) and the side effects knocked me off my feet. I had read on here that the booster wasn't recommended if you had a cold but thought I knew best and had it anyway. I wouldn't do it again. I would delay your booster if you are already off colour

Sorry but they are really, really not. I have had several followed by negative PCRs since August.

Yes, they really, really are that inaccurate. It is hard to calculate exactly because errors can occur in addition to the specificity and sensitivity of the actual test itself and the timing of the test is crucial. But approx 70% accuracy for a PCR is accepted as correct.

Whilst highly specific, PCRs are not very sensitive. This means that they miss approx (maybe up to) 30% of positives.

As with LFT tests however, they are very accurate if they show positive, meaning that you are extremely unlikely to not have Covid after a positive test result:

www.eurosurveillance.org/content/10.2807/1560-7917.ES.2020.25.50.2000568

HOWEVER some people seem to continuously (ie over a period of weeks) show a very faint positive on LFTs with a subsequent negative on PCR, and yes, there have been numerous threads about that on here. There is no data/explanation about the cause of that so far (prior asymptomatic infection?) unless something has been published very recently. If you are one of those people that continuously show positive on LFT and negative on subsequent PCRs then you need to rely on PCRs.

OP is not one of those people though. I would say therefore that very simply, a new, positive LFT AS WELL AS active Covid symptoms means that you have Covid.

In this case if a subsequent PCR shows negative then you need to take another PCR.

I expect that Gov guidelines will change to reflect this.

What @Haffiana said.

Some scientists are suggesting we change to not needing confirmatory PCR for positive lateral flow results as there is no need and it'll free up PCR slots for others.

@JanglyBeads

What *@Haffiana* said.

Some scientists are suggesting we change to not needing confirmatory PCR for positive lateral flow results as there is no need and it'll free up PCR slots for others.

Oh God. I hope they don't go to this system. I have already missed three events where a negtive LFT was required to attend and PCR subsequently negative.

I'm never going to be able to go on an overseas holiday again am I.