Lateral Flow tests

[StrongLegs]

Hi,

I read on here the other day that lateral flow tests are very unreliable - something like 50% false negatives or positives, or something like that

I just wondered, if it's that bad, and we really want to be sure of getting a correct result on a given day, should we just do three tests that day and believe the most consistent result? So:

0 positive results = no covid
1 positive result = no covid
2 positive results = covid infection
3 positive results = covid infection

Sorry, this is slightly tongue in cheek, but not entirely.

My dd is in year 8 and most of the parents have had a phone call to say they have been in contact with a positive case, one of the mums rapid test kept coming back negative, done a pcr out of curiosity and it’s come back positive.
Some rapids came back positive but the pcr was negative! One boy had 3 positive rapids but no symptoms and a negative pcr!! So they aren’t reliable at all in my opinion.
Guidance has changed so if you are identified as a close contact you can get a pcr. So ordered one for my dd to be on the safe side.

If one is positive then it's safe to assume the other 2 are false negatives. False negatives are common, false positives, not so.

Lots of false negatives
Fewer false positives

Thanks, that's good to know :-)

False positives are about one in a thousand.

False negatives maybe one in two (depending on which study, whether self-administered, etc.).

So assume one positive result is a true positive (even if others are negative).

A negative or result may or may not be a true negative and retesting may give yet another result that may or may not be a true negative. The lateral flows aren't really for confirming if you are negative, but more for picking up the occasional asymptomatic positive.

You can't be sure of a correct result unless it's a positive, in which case you can be pretty sure!

I had negative lf the same day as positive pcr so I would agree they are unreliable

I do not trust the lateral flow ones at all, quick frankly it scares me the country is relying on them. Recently me and BIL were I'll with a terrible cold, extreme fatigue etc. Both done lateral flow three times over the 10 days we were sick. He ended up saying he couldn't cope anymore and went to hospital. He had covid pnemonia and his lungs were covered in it. We then had to isolate from the date of his PCR test and not his symptoms as we used lateral flow which was negative.

I can see the arguement that they would get cases that we wouldn't necessarily get but to rely on them for events etc. It's scary.

@katie2812 but your not supposed to use lft with symptoms. You should have done the pcr sooner.

We didn't have any traditional covid symptoms, we just had bad colds that's why we didn't do PCR. We thought well if lateral flow is negative then it's just a cold.

The estimates of the impact of user technique on LFT results are well documented, and can be lower than 40%. If your technique is bad, you could get a whole string of false negatives.

The example you gives falls well within the 'chance' of all the negatives being false.

If you are symptomatic, or get a positive, you need PCR.

Just using more LFTs doesn't tell you what you want it to.

Sadly too many people think that as long as they have negative LFTs they are fine. Kids in DD’s school have come to school with all the Covid symptoms because they’d done an LFT and it was negative.

So cross. In my view giving out the LFTs to everyone does more harm than good.

This is what I feel tbh. Whenever I find myself reaching for a LFT I realise what I should really use is a PCR test.

Also, a relative cheerfully announced to me the other day that she had hayfever and we had a bust-up because I asked her to have PCR test and she didn't want to. I don't think we should be waiting for the fever/cough/taste/smell symptoms now. Anything remotely like a virus gets my hackles up these days.

Totally with @katie2812 on that.