Test results

[Anothernamechangeplease]

Am I right in thinking that a false positive result on a lateral flow test is less likely than a false negative? Or is the likelihood the same for each?

False negative is more likely than a false positive

Cases are rising which means false positives are even less likely than they were a few weeks ago

Thank you.

I had one very strong positive result a couple of days ago, when I was pretty much asymptomatic - perhaps a very slight cough but nothing that I would even register usually. (Tested as a precaution after close exposure.) I have since had two negative tests, but I do now have the worst headache that I just can't shift.

I'm isolating anyway as it's easy for me to wfh and I don't want to pass it on to anyone else, but I'm confused as to whether I actually have it or not. Should I assume from that initial positive test that I do?

A strong positive ( not a faint line) is almost certainly correct assuming you did the test correctly and didn't eat, drink or brush your teeth for half an hour before as some food and drink can give a false positive.

Definitely didn't eat or drink for half an hour before. Can't be 100% sure about cleaning teeth as I didn't realise that was a thing. Don't think so though.

It was a very strong positive line, which is why I was so surprised that I didn't get even a faint line with the subsequent two tests.

Just doubting it a bit as I felt fine the day I took the test. Not feeling great today but part of me thinks that might be psychological...

So confused. I've done a third negative test since my one strong positive. However, my cough is now worse and I have a headache that I just can't shake.

I assume that I have genuinely got covid and that it wasn't a false positive but don't understand why all the LTF tests are coming back negative. Am I doing them wrong?

If you have the Flowflex ones or other type that are nose only, try swabbing your tonsils first. You have to do it quite carefully as the stick is short, but some people will register a positive that way even if they don't with nose only. Apparently it is an Omicron thing?

Thank you @Meowser72. Will try that. Though I'm not quite sure how easy it will be to swab my tonsils with that very short stick. I have a very strong gag reflex!!

Is anyone still testing then?😮

Yes, I am testing. I know lots of people who are quite ill with covid right now, so I don't want to pass it on to anyone else if I can help it. I'm therefore isolating at the moment but I have plans at the weekend that I'd rather not cancel if I don't have to, hence trying to u understand what the negative tests might mean.

Fwiw, most people I know are still testing when they get symptoms. Isn't that just a common sense thing to do?

The rate of false positives doesn't depend on how may cases there are does it, how would that be a factor?

Unless I've misunderstod the whole thing if the false positive rate is (made up figure) 1 out of every 1000 negative people who take a test how is that affected by the number of cases? By definition only a person who doesn't have covid can get a false positive.

It's a thread about testing and results, so I'm going to hazard a guess at 'yes'.
OP, hope you feel better soon and as PP said, it's worth doing nose and throat. Glad you're able to isolate.

It's a mathsy thing which I'm afraid I don't get even though have had it explained a number of times. Because it's a probability we're talking about, if there's very little Covid about then there's more probability of a positive being false than if rates are high. Or something....

Yes, it is quite hard - good luck! I do not even have any tonsils so I had to go in a bit further, if you see what I mean. I did get a positive. Anyway, hope you're okay.

How can that be the case? Only a negative person can get a false positive and the reliability of the test has nothing to do with how many people have covid Those have got to be unconnected

Even if no one had covid the false postive rate would be the same as if 50% of people have it surely

Are you sure you aren't thinking of the false negatives?

I drove myself crazy with this when my son got too false positives in a row ( his were really faint though) back when you could get a PCR to confirm. Generally the false positive rate is about 1/1000 so if 1000 people who are negative do a test one will get a false positive.
Now say that 1% of the population have Covid ( suspect it's actually more at the moment), if 10000 people do a test, 10 will get a false positive but 100 will get a true positive ( this isn't quite right as doesn't account for false negatives but you get the idea). If it's 0.1% of the population then for that 10000 you'll still get the same 10 false positives but only 10 true positives so 50% of the positives will be false.

That is a very good explanation!

But as I have developed quite a cough, I'm guessing that I'm sadly not among the 1 in a 1000 false positive gang. Just the proud owner of lots of false negatives!🙄

Or this explanation, which is even simpler (thanks, Maths teacher pal!)

"If 0% of the population have covid and you do a test and get a positive, you know it's a false positive. If 99% of the population have covid and you do a test and you get a positive then you are pretty sure it's covid. The false positive rate has stayed the same, but the likelihood your positive is a false one decreases the more prevalent covid is."

I don't know. I've never had Covid, and never had symptoms either.
I don't hear people talking about it much any more round our way. We've all moved on through party gate, monkey pox, Rwanda, the war..... and we're all talking about polio now.

I imagine you'll be talking about covid again pretty soon tbh. Case rates here have shot up, and quite a lot of people are quite poorly with it.

I know a few people with it right now. I'm trying to avoid it as we go on holiday on Saturday!