How do lat flows work?

[FuckingFabulous]

I know they detect the antigen which means the virus is present, BUT is that only picked up for a current infection, or will a lateral flow test show positive for ages after you've had the virus? If you had it, had no idea you'd had it and had to take lateral flows for events and holidays and they were coming back consistently positive but PCR negative, does that mean you've had it or that you HAVE it?

If you want a scientific answer, there's plenty of examples online!

My very basic understanding is that if it comes up positive, there's a 99% chance that you are indeed positive. www.gov.uk/government/news/new-analysis-of-lateral-flow-tests-shows-specificity-of-at-least-999

It's more the other way round, where a potential positive could be missed. I'd say this is because you're placing a lot of reliance on people to do the test properly. Here's a link that sort of goes into a bit more detail.. www.rcpath.org/discover-pathology/news/accuracy-of-lateral-flow-antigen-tests-for-covid-19.html

Additionally, and I don't condone this at all, but they are very VERY easy to rig....

I have shown positive on lateral flow for two weeks, but negative on PCR. Five weeks ago, I was also repeatedly positive on lateral flow but negative on PCR, so I stopped testing. These aren't lines that require an inversion tool or eagle eyed vision to see either, they're very very clear. So, have I had the virus all this time?? Have I repeatedly had it? Did I have it, not know and this is all residual? Or is there something weird about me that means I test positive on it? It's hard to know what I should be doing. Certain events coming up won't let you in unless you can show a negative lat flow on the day, regardless of vaccination status, and I obviously can't but I don't know why, considering I've repeatedly been shown by PCR to be negative

Are you following the instruction to not eat or drink for 30 minutes before testing?

@FlagsFiend

Are you following the instruction to not eat or drink for 30 minutes before testing?

Yes. Test first thing in the morning before I've had anything at all. They're always positive.

How odd, do they go strongly positive straightaway or take ages for the test line to appear? I've only ever had negatives and the control line (the top line if you are positive) appears as the liquid travels up. Does the test line appear as quickly or take longer to develop?

I wonder if you have a bad batch of tests...

Ring 119 although I bet they just give a standard answer.

@FlagsFiend

How odd, do they go strongly positive straightaway or take ages for the test line to appear? I've only ever had negatives and the control line (the top line if you are positive) appears as the liquid travels up. Does the test line appear as quickly or take longer to develop?

I wonder if you have a bad batch of tests...

I've taken them all from different boxes, it appears either straight away or within the first ten minutes, still visible at 30, anything from bright pink lines that match the control to about half that intensity.

I've even asked relatives to drop me some of their lateral flow tests because I was getting paranoid that the ones I had were compromised in some way. But it's nobody else in the house. Just me. PCRs have been negative. Lateral flow always positive. No matter when I take them. I've even used the same sample and dropped on separate tests from separate boxes. A couple of drops on each, both positive to pretty much the same intensity

I was told lateral flows are positive for up to 90 days after you’ve had Covid…so it’s possible you had it and didn’t realise in the last couple of months. That could be the answer to positive lateral flows but negative PCR tests.

This research suggests the6 are just as effective as PCR.