The 'I have some sort of lurgy but don't know if it is corona or just a cold' thread

[IC3D]

So I have done 5 lateral flow tests over the last week, they were all negative.

What do you think is the likelihood that I actually have Covid that has been missed by 5 tests, rather than RSV - which is what I think I have.

IC3D - I hope your niece recovers quickly, there is a massive spike in cases but it can be more serious in babies and toddlers so best wishes for the little'un. xx

Thank you she's fine now. Hope you feel better soon.

 

[Epona]

Thank you she's fine now. Hope you feel better soon.

I am recovering fine, thank you, I had a couple of days when it was a bit shit and I didn't feel like eating and it affected my ears and my balance last night. I feel a lot better this morning though, thank you!

My OH has also caught it (he also does lateral flow tests for work and has been testing negative for Covid), it is a bit worse for him because he has severe (brittle) asthma so it affects him a lot worse.

 

[Thora]

I don’t think anyone can give you an exact likelihood. It’s not uncommon for people who test positive on a pcr to have had multiple negative lateral flow results though.

 

[2hats]

You'd need to perform at least three NHS rapid home (Innova) LFD tests together at a time, properly*, daily for 5-7 days after exposure to be reasonably sure (96%) you were not getting false negatives (obviously stop as soon as you get one positive result and follow up with PCR to confirm).

* A significant proportion of self-trained public tend not collect an adequate, 'clean' samples.

 

[Mogden]

You'd need to perform at least three NHS rapid home (Innova) LFD tests together at a time, properly*, daily for 5-7 days after exposure to be reasonably sure (96%) you were not getting false negatives (obviously stop as soon as you get one positive result and follow up with PCR to confirm).

* A significant proportion of self-trained public tend not collect an adequate, 'clean' sample.

Interesting. I've got pink eye, a sore throat of a tonsillitis variety, lots of coughing and have been ridiculously achy. LFT and PCR negative. No one has suggested daily LFT and frankly I'd be happy to do that to get to the bottom of what it is. I was on hold for a full hour this morning for a doctor's appointment and that only got me a call back later on today. I need to be back at work tomorrow, had a full week of annual leave wasted on staying in being ill, and need to know if I'm safe to return.

 

[Epona]

You'd need to perform at least three NHS rapid home (Innova) LFD tests together at a time, properly*, daily for 5-7 days after exposure to be reasonably sure (96%) you were not getting false negatives (obviously stop as soon as you get one positive result and follow up with PCR to confirm).

* A significant proportion of self-trained public tend not collect an adequate, 'clean' sample.

What is the point of doing lateral flow tests as mandated by an employer to make sure you are allegedly safe for work then? It sounds like it is mostly about employers getting off on getting people to swab their tonsils twice a week for absolutely no good scientific reason (which tbh would not surprise me).

But IF they are so innaccurate, why are we bothering to do lateral flow tests? What is the point if I do one but according to "people on the internet" I cannot trust the negative result? Why is the NHS distributing them? Why are employers using the results to determine whether someone is safe to go into work or not?

 

[IC3D]

Not diagnosing Mogden but RSV definitely possible as you had conjunctivitis with those symptoms.

 

[Thora]

What is the point of doing lateral flow tests as mandated by an employer to make sure you are allegedly safe for work then? It sounds like it is mostly about employers getting off on getting people to swab their tonsils twice a week for absolutely no good scientific reason (which tbh would not surprise me).

But IF they are so innaccurate, why are we bothering to do lateral flow tests? What is the point if I do one but according to "people on the internet" I cannot trust the negative result? Why is the NHS distributing them? Why are employers using the results to determine whether someone is safe to go into work or not?

You're only supposed to use them if you have no symptoms. You are ill though, right?

The point of doing them is that they pick up some asymptomatic cases that otherwise wouldn't be picked up.
They aren't used to diagnose your illness.

 

[zahir]

What is the point of doing lateral flow tests as mandated by an employer to make sure you are allegedly safe for work then?

They should pick up a lot of covid infections in people who don't have symptoms and would otherwise have no reason to get tested.

 

[prunus]

What is the point of doing lateral flow tests as mandated by an employer to make sure you are allegedly safe for work then? It sounds like it is mostly about employers getting off on getting people to swab their tonsils twice a week for absolutely no good scientific reason (which tbh would not surprise me).

But IF they are so innaccurate, why are we bothering to do lateral flow tests? What is the point if I do one but according to "people on the internet" I cannot trust the negative result? Why is the NHS distributing them? Why are employers using the results to determine whether someone is safe to go into work or not?

They are an imperfect tool, to be sure.

They will actually pick up less than half of actual positive cases it appears from real-world studies.

Their use is that those that they do pick up - symptomless people on the whole with regular testing (ie tests done not because you felt ill but because you were just doing them twice a week) can take themselves out of circulation and not spread infection, which they wouldn’t know to do otherwise.

If everyone was doing them all the time we could reduce asymptotic carriers in the community by about 40% (approximate real-world sensitivity).

If one has any suspicion one might actually have covid one should do a pcr test, not a lateral flow - the overall ability of lfts to give accurate results actually goes down if you have symptoms (because of complex things to do with conditional probability - I think! It’s a while since I was fully on top of that).

They do have a use - but the use is not to rule out if someone does have covid - it’s to rule out that someone doesn’t have covid.

 

[Epona]

You're only supposed to use them if you have no symptoms. You are ill though, right?

The point of doing them is that they pick up some asymptomatic cases that otherwise wouldn't be picked up.
They aren't used to diagnose your illness.

How on earth can they be providing positive results for non-symptomatic cases yet are not sensitive enough to detect a coronavirus case in someone who is unwell? You are talking absolute nonsense.

Also I do not have COVID and I do not have any suspicion that I have COVID.

 

[Thora]

How on earth can they be providing positive results for non-symptomatic cases yet are not sensitive enough to detect a coronavirus case in someone who is unwell? You are talking absolute nonsense.

OK angry lady. Hope you have a great day.

 

[Epona]

OK angry lady. Hope you have a great day.

You too my love - take care and live your life as best you can. xx

 

[Orang Utan]

Epona you really need to get a PCR test, LFTs are for non-symptomatic folk

 

[Epona]

Epona you really need to get a PCR test, LFTs are for non-symptomatic folk

I don't understand how an LFT can detect coronavirus in someone with no symptoms, but if someone is unwell it is not going to detect coronavirus in them. Explain it to me, please! I want to understand.

I don't have symptoms of Coronavirus anyway.

 

[Mogden]

Doc has phone diagnosed viral infection and signed me off for a week. Usual paracetamol, plenty of fluids, if it gets worse call them back.

 

[prunus]

I don't understand how an LFT can detect coronavirus in someone with no symptoms, but if someone is unwell it is not going to detect coronavirus in them. Explain it to me, please! I want to understand.

I don't have symptoms of Coronavirus anyway.

It's sort of complicated, and not quite as black and white as that, but I'll have a go (caveat: I may be wrong!).

There are two aspects to the question - one is the mechanics and efficacy of the test itself, the other is mathematical and about statistical sampling and how it affects results.

The first is easier to talk through: The way the LFT works is by detecting coronavirus proteins picked up on the swab. It needs a certain amount of that protein to be able to detect - too little and it just won't show up.

The amount of protein picked up on the swab depends on a number of factors: the amount of viral protein in the subject (ie viral load); the amount of protein in the subject in the location the swabs are taken (the primary locus of the infection moves around, and is different in different people); the skill of the person in being able to sample the proteins.

The first one of these is generally going to be correlated with symptomatic status - but it's not a perfect correlation - it's entirely possible for someone with symptoms to have a lower viral load than someone without. This on its own can lead to the situation you are asking about.

The second one adds more uncertainty to the first - for instance someone with severe lower lung infection might not actually have much virus left in their upper airways (different immune responses affect the upper airways), so they might be really quite ill, but not have enough protein in the nose/throat to be able to detect it. Similarly with heavy gut load infection, or other patterns of infection (this is quite correlated with the time in the course of the disease the sample is taken - early infections tend to be more in the upper airway, and it migrates down into the rest of the body if the infection is not checked).

The third aspect then adds more uncertainly again - even if an unwell person has high viral load in the upper airways, they might just not be very good at swabbing (it's not easy to do right without having been shown). This is a systematic effect - ie someone who's not very good at it will probably be not very good at it every time they try, so continually fail to pick up a positive result.

Hope that all makes some sense - I will have a go at the conditional probability part of the question later on when I've had some time to remind myself how it works

 

[2hats]

I don't understand how an LFT can detect coronavirus in someone with no symptoms, but if someone is unwell it is not going to detect coronavirus in them. Explain it to me, please! I want to understand.

Because of the wide range of presentations in the infected twinned with LFT being useful during a relatively narrow window and blurred by the competence of the person carrying out the test.

You can have high viral load and be infectious without symptoms or prior to developing symptoms. You can have symptoms for days, indeed weeks after the window where you would have tested LFT positive.

A not untypical infection timeline looks something like:

(Note that delta has, probably, typically skewed that red viral load line to the left by up to 2-3 days in many individuals, though not all).

Additionally a not insignificant number of the public don't sample adequately and/or contaminate the sample.

So one needs to test very carefully, multiple times and daily from shortly after the suspected time of exposure. If you happen to test correctly at the right time in the window then you can (does not equal will) get a true positive from a single test.

 

[Epona]

I have tested multiple times though, I am not some sort of idiot.

I worked in Defra for years dealing with tests from animals, I am perfectly able to test myself properly. OH was a nurse for 20 years and has a qualification in immunology.

We aren't some sort of idiotic loonspuds.

 

[elbows]

I don't understand how an LFT can detect coronavirus in someone with no symptoms, but if someone is unwell it is not going to detect coronavirus in them. Explain it to me, please! I want to understand.

I don't have symptoms of Coronavirus anyway.

Its not that LFTs cannot detect cases in people with symptoms. Its that LFTs arent accurate enough in general to be able to say that negative LFTs provide highly accurate assurance that someone isnt positive.

So they are being used to pick up a proportion of positive cases that would otherwise not have been tested at all at that time due to a lack of symptoms. Because thats deemed to be better than nothing, they are picking up some cases that would otherwise have been missed. But if they were used instead of PCR tests in people with symptoms, they would miss more positive cases than PCR tests would, so they would be doing more harm than good. They can also do more harm than good if people who would otherwise have assumed they might have Covid and adjusted their behaviour as a result, instead assume that a negative LFT result means they can be highly confident they dont have Covid.

 

[elbows]

I have tested multiple times though, I am not some sort of idiot.

I worked in Defra for years dealing with tests from animals, I am perfectly able to test myself properly. OH was a nurse for 20 years and has a qualification in immunology.

We aren't some sort of idiotic loonspuds.

People mentioning stuff about the public not doing the tests properly is not a judgement on you personally. Its because that aspect was one of the very important things that were picked up in trials of these tests being used for mass population testing during outbreaks. Its a headline factor in some very sensible scientific studies of this, it cannot be ignored when discussing the strengths and limitations of this form of testing.

 

[elbows]

PCR tests arent immune from all of these issues either, they just arent as bad as LFTs in certain specific ways.

So for example whenever anyone on this forum has said 'oh I didnt have covid after all, my PCR test was negative', I have been tempted to say 'thats not actually 100% proof that you dont have covid'.

 

[Mogden]

I just use PCRs and LFTs as proof of my due diligence rather than a concrete actual negative result.

 

[Epona]

Its not that LFTs cannot detect cases in people with symptoms. Its that LFTs arent accurate enough in general to be able to say that negative LFTs provide highly accurate assurance that someone isnt positive.

So they are being used to pick up a proportion of positive cases that would otherwise not have been tested at all at that time due to a lack of symptoms. Because thats deemed to be better than nothing, they are picking up some cases that would otherwise have been missed. But if they were used instead of PCR tests in people with symptoms, they would miss more positive cases than PCR tests would, so they would be doing more harm than good. They can also do more harm than good if people who would otherwise have assumed they might have Covid and adjusted their behaviour as a result, instead assume that a negative LFT result means they can be highly confident they dont have Covid.

I don't have coronavirus symptoms though, if I was then fair enough but people on this thread are being a bit dictatorial about it when I don't have symptoms (it is very easy for people to tell other people what to do and get their knickers in a twist about it), OH doesn't have symptoms, we've both done a load of lateral flow tests, I am pretty much better now and I am not doing any more fucking tests. I barely leave the house anyway so it is academic.

(Seriously, if I do not leave the house, what is the point of getting a pcr test except just for my own interest? I don't work, I am not going anywhere)

Seriously there is a whole world of anti-vaxxers out there, if anyone is getting upset that someone who is double jabbed and rarely goes out is using a lateral flow test rather than a pcr test every time they leave the house (on the rare occasion that they do) then they need to fucking get a life.

 

[elbows]

Everyones motivations were good, but its also understandable that such words may rub people up the wrong way.

 

[Orang Utan]

I don't have coronavirus symptoms though, if I was then fair enough but people on this thread are being a bit dictatorial about it when I don't have symptoms (it is very easy for people to tell other people what to do and get their knickers in a twist about it), OH doesn't have symptoms, we've both done a load of lateral flow tests, I am pretty much better now and I am not doing any more fucking tests. I barely leave the house anyway so it is academic.

(Seriously, if I do not leave the house, what is the point of getting a pcr test except just for my own interest? I don't work, I am not going anywhere)

Seriously there is a whole world of anti-vaxxers out there, if anyone is getting upset that someone who is double jabbed and rarely goes out is using a lateral flow test rather than a pcr test every time they leave the house (on the rare occasion that they do) then they need to fucking get a life.

we just want you to be healthy and the official advice is if you have any cold-like symptoms then you get a PCR. so best follow official advice to be safe and sure.

 

[Epona]

we just want you to be healthy and the official advice is if you have any cold-like symptoms then you get a PCR. so best follow official advice to be safe and sure.

Ty that is a very nice message and thought, I appreciate it

I am fine, I had a mild sinus thing last week, which over the weekend seemed to turn into an ear infection with related vertigo and a case of the rampant shits (sorry for the TMI) - it honestly doesn't seem to bear any resemblance to the list of Coronavirus symptoms, my digestive system is still playing up a bit but I am sure I will be fine. It is all compounded by a horrible sleep pattern which is always a difficult thing for me - I feel a bit spaced out due to lack of sleep/sleeping at odd times and not eating properly for a few days as I haven't had the energy to cook and my gut has been playing up - OH got some pizza into me this morning though when he was having his own dinner and I have started to feel a lot better.

 

[wemakeyousoundb]

Ty that is a very nice message and thought, I appreciate it

I am fine, I had a mild sinus thing last week, which over the weekend seemed to turn into an ear infection with related vertigo and a case of the rampant shits (sorry for the TMI) - it honestly doesn't seem to bear any resemblance to the list of Coronavirus symptoms, my digestive system is still playing up a bit but I am sure I will be fine. It is all compounded by a horrible sleep pattern which is always a difficult thing for me - I feel a bit spaced out due to lack of sleep/sleeping at odd times and not eating properly for a few days as I haven't had the energy to cook and my gut has been playing up - OH got some pizza into me this morning though when he was having his own dinner and I have started to feel a lot better.

good to read, just lookafter yourself even if you don't feel like it

 

[Looby]

I have earache, have a bit of deafness and a sore throat. Plus a headache and feeling tired.
Not the big three symptoms but definitely possible Covid symptoms.
LFTs continue to be negative but I’ve done a PCR and waiting for the results.

For general info, cold symptoms and upset stomach are very common Covid symptoms.

 

[Puddy_Tat]

came over feeling quite hot yesterday evening (it wasn't all that warm here)

woke up with sore throat, sniffles, headache, and general aches and pains and crappiness.

did a LFT test on Sunday and all clear but...

booked a drive-in PCR test for later.

bugger.