Active discussions

Meet the Other Phone. A phone that grows with your child.

Meet the Other Phone.
A phone that grows with your child.

Buy now

Please or to access all these features

Talk
AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Original poster

Dd is sick, lateral flow negative, PCR necessary?

37 replies

ThesecondLEM · 18/09/2021 17:00

Do I need to get PCR? Local testing centre is 20 miles, she is really poorly and has slept all day?

Obviously I will keep her out of school as if she is positive. She has had covid before but I know that means nothing, I am assuming that she has it again? Will do daily lateral flow tests

OP posts:
Blastandbollocks · 18/09/2021 17:01

LFT for asymptomatic people. If you have symptoms you need a PCR.

AtrociousCircumstance · 18/09/2021 17:01

Lateral flow tests are for when there are no symptoms. PCR for symptoms.

cameocat · 18/09/2021 17:02

If she has any of the following you need a pcr:
Raised temperature
New cough
Loss of sense of taste or smell

This guidance has not changed

Original poster
ThesecondLEM · 18/09/2021 17:02

Oh, bugger. OK I will book her in.

OP posts:
Seeline · 18/09/2021 17:03

Needs a PCR if she has one or more of the three symptoms

Unicornhorns · 18/09/2021 17:04

DS was extremely sleepy and had a positive LFD, he then had a very mild fever (37.5 - 37,7), his PCR was positive.

Original poster
ThesecondLEM · 18/09/2021 17:05

We didn't get her tested last time as we all had it, dp and myself tested positive so seemed pointless. We were all isolating.

The guidance has changed though, I don't have to isolate as I'm double jabbed which is weird if you ask me.

OP posts:
brazenandstrange · 18/09/2021 17:05

Can anyone tell me why a lateral flow won't pick up the virus if you already have symptoms? Surely that would be positive if you're in the first couple of days of having symptoms?

EatYourVegetables · 18/09/2021 17:06

You can get a test delivered to your house, take it and mail it. Saves the hassle of droving 2x20 miles with a sick child. Tests delivered by Royal mail the next day, you do the test at home (similar to how you do LFT), send them for free using special mailboxes (there are loads of them where I live, you can check ahead of time on Royal Mail web), and the results come in very quickly after sending (was

RampantIvy · 18/09/2021 17:06

Can you order a PCR online to be posted to you?

Original poster
ThesecondLEM · 18/09/2021 17:07

A friend of mine had cold symptoms, tested negative until day 3 then tested negative.

I don't think LFT picks up low levels of virus

OP posts:
EatYourVegetables · 18/09/2021 17:08

@ brazenandstrange It might pick it up but it might not. So it’s not reliable enough to be used on people with symptoms because of a high rate of false negatives.

The effectiveness of the LFT doesn’t change depending on whether you have symptoms, but people with symptoms need a more reliable test than people without symptoms.

Original poster
ThesecondLEM · 18/09/2021 17:08

@EatYourVegetables oh that's really helpful, thank you I'll send for that now.

OP posts:
MsAwesomeDragon · 18/09/2021 17:09

@brazenandstrange

Can anyone tell me why a lateral flow won't pick up the virus if you already have symptoms? Surely that would be positive if you're in the first couple of days of having symptoms?
The lateral flow tests just aren't sensitive enough to pick up all infections. If you get a positive LFT then you're not than likely to have it, but if you get a negative LFT that means you could still have it but the test has missed it.
MrsAvocet · 18/09/2021 17:12

My DS started feeling non specifically unwell on Weds afternoon.LFT was negative. By Thursday morning he was coughing so we took him for a PCR which was positive. My adult DD also had a negative LFT and a positive PCR and I have heard of quite a lot of similar experiences. I would get it done if I were you. The postal ones take a bit longer obviously but only a day or two so you could do that if you dont want to go to a testing centre. Hope she feels better soon.

Dunrovi · 18/09/2021 17:13

@brazenandstrange

Can anyone tell me why a lateral flow won't pick up the virus if you already have symptoms? Surely that would be positive if you're in the first couple of days of having symptoms?
It might well show up. Certainly did for my Dd and her friend who both thought they had a cold. All they're saying is that it's not as sensitive as a PCR test so you can't trust a negative LFT as a definitive answer as to whether the symptoms you are suffering are Covid or not.
jacks11 · 18/09/2021 17:15

Lateral flow tests have a high false negative rate (some studies suggest as high as 48%)- if you have symptoms you need a PCR to be sure you are negative. Equally, if you have a positive lateral flow, you need a confirmatory pcr as you can have positive lateral flows for weeks after infection has resolved.

In short- lateral flows are screening tests and the PCR are the more accurate diagnostic tests.

EatYourVegetables · 18/09/2021 17:23

@brazenandstrange

Mathematically this is what happens. (I will make up all the numbers but you can get the idea from them, they are very approximately right.)

The LFT has something like 20% false negatives, meaning that in about 20% of infected people it incorrectly gives a negative.

If you give such a test to a group that is likely to be infected, that will be a lot of false results. Eg, take a group of 1000 people with symptoms such that 500 of them don’t have covid and 500 have covid. Say they all take LFT. It will tell all 500 people without covid that they are negative, it will tell 400 of the people with covid that they are positive, and it will tell 100 of the people with covid that they are negative. So you end up with 100 people with covid walking around convinced they are negative and spreading it (bad).

If you give this test to a group which is not likely to have covid, you will get fewer false negatives. Eg, take a group of 1000 people with no symptoms, and in that group 10 people have asymptomatic covid and 990 don’t have covid. The test will correctly say that 990 are negative, it will tell 8 asymptomatic people with covid that they are positive, and it will tell 2 asymptomatic people with covid that they are negative. So, you end up with 2 people walking around with covid convinced they are negative and spreading it (which is bad but not as bad as having 100).

Hope this helps.

tigger1001 · 18/09/2021 17:25

When did the rest of you test positive? If you suspect she was positive in the last 90 days you shouldn't do a pcr as could be a false positive.

Snufkin2 · 18/09/2021 17:33

@ThesecondLEM

We didn't get her tested last time as we all had it, dp and myself tested positive so seemed pointless. We were all isolating.

The guidance has changed though, I don't have to isolate as I'm double jabbed which is weird if you ask me.

If hers is positive you should still isolate till you have a PCR yourself. The difference now is that you don't have to then continue to isolate if yours is negative and you're fully vaccinated.
Original poster
ThesecondLEM · 18/09/2021 17:40

Thanks guys, have sent for a PCR for her.

OP posts:
FlatteredFool · 18/09/2021 17:49

Lots at school have had negative lfts followed the next day by positive PCRs. No symptoms.

Original poster
ThesecondLEM · 19/09/2021 15:52

We decided to drive to the test centre in the end as DD is wanting to return to school as soon as she can and we can't get a pcr unless she is positive. I am still expected to go to work though and the guidance confirms that this is OK 🤷‍♀️

OP posts:
Moraxella · 19/09/2021 16:08

@ThesecondLEM it’s mad isn’t it, my OH PCR positive and I had to go to work (in a hospital) and then positive three days later 🤦‍♂️

NuffSaidSam · 19/09/2021 16:13

'we can't get a pcr unless she is positive'

That's not correct you can get a PCR if you have symptoms, regardless of LFT results.