Lft negative, pcr positive

[Bennetgirl]

Dn has tested positive today on a lft as he has a snotty nose. All other lfts this week have been negative.( Testing every day)

He had a home pcr test on Tuesday which has just come back positive. He has been in close contact hence the tests.

Doesn't this make lfts pointless? He's been testing negative with no symptoms but has been infected. He only tested positive on one once he was ill.

LFT are not for people with symptoms

PCR are more sensitive.

He'd been testing with lfts every day as his school is bad and they were all negative until he had a symptom.

The pcr was done before the symptoms started.

PCRs are more effective then LFTs hence why anyone with symptoms must take a PCR.

The theory is a LFT picks up 5 out of 10 cases with no symptoms, it’s 5 cases that would have other wise been missed completely.

I had 5 lft negative but applied for postal pcr and positive

I put a lot of trust in lfts! I certainly won't anymore.

I have since done home lft tests and if you wait the full 30 mins a faint line does appear, but it's really faint.

It's not an all or nothing thing though, it isn't true that LFTs are of no use at all. They just have lower sensitivity than PCR tests.

How do people still not understand this

The point of LFTs is to show when your viral load is highest and most infectious. A pcr is more sensitive and will give a positive when you are infected but may have a low viral load and not actually be infectious.

If symptoms had not meant he was eligible for a PCR, then the LFT which was positive today would have meant that he was now eligible for PCR. So the LFT is useful in picking up some cases.

In his specific case, he had the PCR before the LFT was positive, and the PCR result was positive.

A negative LFT is not to be trusted. That has always been the case, hasn't it. Have people not understood that. LFT is good in terms of having a low false positive, so if it shows positive it is very very likely that someone is positive. A negative LFT though means very little, as there is a high false negative rate.