Can anyone help me make sense of this please!!!

[mrsdolittle]

Sorry - bit of a back story but I'll try and keep it brief. Last weekend I visited a venue that was covid positive (think hospital type scenario). I wasn't there long and wore PPE. But I thought it wise to take a PCR on Wednesday and also booked one for DH because obviously he has been in close contact with me. We had both been doing LFT's since the weekend - always negative. Anyway the results came back Thursday. I tested negative but DH was positive!! He immediately did another LFT which was again negative.

He's obviously now self isolating and did the T&T thing but I am completely baffled as to why his LFT's are still negative (we've both been doing them everyday since - always negative).

He really doesn't have any symptoms to speak of - a bit of a cough (but he has a cough anyway due to meds he takes) and possibly bit achy. But tbh if he hadn't had the positive result there would be no real reason to think he has covid.

I've since done another PCR and I was negative.

I'm not suggesting his positive PCR is wrong - I understand that is highly unlikely. But am really confused as to why the LFT's are always negative.

Has anyone experienced anything similar please?

LFTs are not reliable at all. They are more likely to give a false positive rather than the negative but you have done the right thing by getting PCRs.

They are very unreliable.

@Finfintytint

LFTs are not reliable at all. They are more likely to give a false positive rather than the negative but you have done the right thing by getting PCRs.

So it's quite feasible that some one with active covid might never test posting on a LFT do you think?

I think it’s more likely to test positive rather than negative but just assume LFTs are unreliable either way. I do them twice a week because work demands it. I just go by who I have been exposed to and symptoms as to when I do a PCR.

I think lateral flow tests are far less sensitive. So if he has a really mild case there is less of the virus to detect. So totally possible to test repeatedly negative on them but actually be positive.

Note: not based in real scientific or medical knowledge, just my understanding of it.

piggywaspushed had really bad covid but never tested positive on an LFT.

Lfts are notoriously unreliable. Sometimes they will catch some positives but half the time they won’t pick it up at all unfortunately.I think your situation is quite common.

@SummerHouse

I think lateral flow tests are far less sensitive. So if he has a really mild case there is less of the virus to detect. So totally possible to test repeatedly negative on them but actually be positive.

Note: not based in real scientific or medical knowledge, just my understanding of it.

That would make sense.

DS had covid a couple of months ago and he didn't test positive on LFT until he was proper poorly. So if DH has a mild case it might never show on LFT

Bloody scary though to think how many people are relying on LFT results when actually they are positive. No wonder covid is spreading like wildfire. I guess they do work most of the time but even so

My DH tested positive last week. It took me 5 days, 2 PCRs and 2 LFTs to get a positive test (PCR last Saturday) and I was symptomatic. Apparently I was free to bowl around infecting people in that time. It luckily I used my common sense and self isolated anyway.

I had heard this happening to lots of other people (on MN mainly!!) so I knew the tests were likely to be wrong, which they were.

Still feeling poorly :-(

@RavingAnnie

That's really interesting. Sorry to hear you are still poorly

Thanks @mrsdolittle feeling a bit fed up with it now.

I've booked yet another PCR for tomorrow. I am expected in work on Tuesday regardless of DH's covid status (I'm double jabbed) and I really really don't want to spread covid around my office. Particularly as a colleague I work closely with would probably be pretty poorly with covid.

Will be my third PCR in a week but no one seems to be counting!

@Finfintytint

LFTs are not reliable at all. They are more likely to give a false positive rather than the negative but you have done the right thing by getting PCRs.

Is this actually true?

@Finfintytint

LFTs are not reliable at all. They are more likely to give a false positive rather than the negative but you have done the right thing by getting PCRs.

You have that the wrong way round. LFTs are more likely to give a false negative than a false positive.

LFTs are shit, I've recently had Covid and all my LFTs were negative. I did loads. Apparently they only work if you have a very high viral load. My Covid symptoms were quite mild.

It may not be the LFTs that are shit, rather the people doing them are not very good at it.

As someone just said, it is much more likely to be the other way round. False negatives are more likely than false positives.

I tested negative on an LFT on Tuesday twice, then positive twice on the Wednesday. Not because they are shit but because It was too soon - like a pregnancy test.

Thank you all so much.

This is so helpful and reassuring.

Is it possible that your DH has had covid within the past few months (perhaps when your DS had covid, or another time entirely)?

PCR tests will come back as positive for up to 90 days after infection, I think because they also detect fragments of dead virus.

LFTs only detect live virus, so in theory they show a negative result as soon as you've cleared the infection.

@Finfintytint

LFTs are not reliable at all. They are more likely to give a false positive rather than the negative but you have done the right thing by getting PCRs.

No - they give a lot of false negatives and very few false positives.

@WaltzingToWalsingham

Is it possible that your DH has had covid within the past few months (perhaps when your DS had covid, or another time entirely)?

PCR tests will come back as positive for up to 90 days after infection, I think because they also detect fragments of dead virus.

LFTs only detect live virus, so in theory they show a negative result as soon as you've cleared the infection.

That is indeed possible. It had occurred to me. We both did PCR's in the middle of July when DS had covid and we were both negative. But yes he could have caught covid anytime between that test and now - but so mild that it didn't show on LFTs. And if it was/is a very mild case he wouldn't necessarily pass it on to me. Certainly a plausible scenario

A friend's son felt grotty and did a LFT - positive.
His mum booked him for a PCR.
In the couple of hours before the PCR, his mum began to feel ill and did a LFT - negative.
She booked her and her husband in for PCRs as well.
All three tested positive on the PCRs.
Her son did another LFT five days later - still positive.
Mum and asymptomatic dad did LFTs on day 5 and day 9 - all negative.

@Scarby9

A friend's son felt grotty and did a LFT - positive. His mum booked him for a PCR. In the couple of hours before the PCR, his mum began to feel ill and did a LFT - negative. She booked her and her husband in for PCRs as well. All three tested positive on the PCRs. Her son did another LFT five days later - still positive. Mum and asymptomatic dad did LFTs on day 5 and day 9 - all negative.

Just so random!

The LFT has a "sensitivity" of 57%, which means that if you gave 100 people with Covid a LFT, it would pick up 57 of them.

I understand it's to do with viral load - LFT needs a higher viral load that PCR to test positive. If that's the case, then if someone has Covid but a low viral load, it's quite feasible for him to keep testing negative on LFT.

It may sound as if LFTs are no use, but on a population scale it makes sense - for example, imagine 800 people going to an event. At current levels, 10 of them may have Covid. If they all take a LFT, then 5 of those may test positive, and you've reduced the number of people with asymptomatic Covid wandering around the event from 10 to 5 - worth doing.

On the other hand, the chance of a false positive is, if I remember correctly, about one in 200, so there'll be 3 - 4 unfortunate people missing the event even though they don't have Covid.

Of course, if the rate of Covid fall from 1 person in 80 to, say, 1 person in 160, things get interesting. There will now be only 5 people hoping to attend the event who have Covid, and LFT will pick up 2 or 3 of them. But it will still pick up 3-4 of the 795 perfectly well people as false negatives. So we'd be in the bizarre situation that if you tested positive on LFT, then you're actually more likely not to have Covid - a situation that gets worse and worse as the frequency of Covid decreases. Which I imagine is why the government asks you to get a PCR test if you have a positive LTF.

@MereDintofPandiculation Thank you. That is fascinating - and very well explained.

I won't write off LFT's just yet then!