Lateral Flow Tests Timings (UK)

[RobertCLL]

I tried to find the answer online but was unsuccessful.

My question is, on day 1 you are exposed to covid, how long would it be for a lateral flow test to show the positive result?

I just trying to establish timings for our son who has been self isolating with us for the last 18 months. He has to go to London for a day, then return to his house in Woking, then after self isolation/LFT test return home to us. It's this time that I need to know.

[Newdawn Administrator]

People who have COVID-19 can infect others from around 2 days before symptoms start, and for up to 10 days after. They can pass the infection to others, even if they have mild symptoms or no symptoms at all, which is why they must stay at home.The recommendation for precautionary asymptomatic testing is every 3-4 days. The most infectious period is thought to be 1 to 3 days before symptoms start, and in the first 7 days after symptoms begin. But some people may remain infectious for longer depending on severity of viral load.

It’s hard to recommend when the best time is for an asymptomatic person to test but a test before visiting and 3 days later sounds to be in line with the advice I’ve read (and I’ve been doing LFT’s because I developed symptoms).

Detection of the virus doesn’t necessarily mean the person is infectious which complicates matters even further!

You’re right in saying a search for specific guidance on when a LFT will pick up infection yields little definitive advice. However, I found this article useful and it’s clear that LFT’s are pretty accurate at picking up early infection at the onset of symptoms. That’s why I’d advise testing before visiting and again within 3 days but this is purely advice based on my own research. There’s clearly variables dependent on viral load and the accuracy of self assessment etc. As you can get a pack of 7 LFT’s free, your son could do a daily test if it felt more reassuring.

ox.ac.uk/news/2021-07-14-la...

Best wishes,

Newdawn

[RobertCLL in reply to Newdawn]

Thank you. 3 days should be fine.

[bennevisplace in reply to RobertCLL]

As they are plentiful and free, I would ask your son to do a daily test. That's because the more tests that are crammed into the risk period, the lower the chance of dangerous false-negatives. With the NHS test kit the real world sensitivity is only about 50 % +/-. meaning the risk of a false negative is also 50 % -/+ per test. After 5 tests this risk falls to ~ 3 %.

It wouldn't be a bad idea to do a PCR test too, on the basis that he will be sharing a house with someone clinically vulnerable.

[RobertCLL in reply to bennevisplace]

Thank you. Daily tests makes sense. Will look into PCR tests.

[Vindicatrix in reply to Newdawn]

Very helpful chat Newdawn, as I am off on a 2 week holiday holiday to London and South. Will be taking Lateral Flow tests dailty, wearing FFP2 masks, no hugging, and dining outside, staying away from groups of people. Keeping distance, and frequent washing of hands. I also squirt some 'Taffix' nasal spary up my nose, and use a dilution of 'Mosiguard' Anti Mosquito spray with a good hand sanitiser. I can't think of anything to add, unless you or anyone else have any suggestions.