Will an LFT at 10 days be negative?

[coviduality]

My whole family tested positive for covid last Tuesday, symptoms started Monday.
We are at home isolating, we are allowed out on Thursday 2nd Dec.
On Friday 3rd, we have plans to go for the weekend to my sister's, along with my parents etc, 14 of us in total.
Parents and sister are quite concerned that we will only just have come out of isolation, and may still be infectious.
They would like us to take LFTs, and only come if they are negative.
I am worried that they could be positive even if we're no longer infectious, and am feeling that this extra measure is unnecessary. Obviously though, I don't want to risk infecting my parents!
Has anyone done this? Anyone still positive on lft after 10/11 days?
I know we're not meant to take a pcr for 90 days, but LFTs work differently?

I can only find the 90 day thing in the outbreak in a care home setting but don't see how that would differ from any other setting;

The 90-day window after a positive test

If someone has tested positive with a PCR test, they should not be tested using either PCR or rapid lateral flow tests for 90 days, unless they develop new symptoms during this time – in which case they should be retested immediately using PCR.

This 90-day period is from the initial onset of symptoms or, if asymptomatic when tested, their positive test result.

www.gov.uk/government/publications/coronavirus-covid-19-testing-in-adult-care-homes/covid-19-testing-schedule-for-a-suspected-or-confirmed-outbreak-in-a-care-home

Mine took until day 14 to go negative. I'd had both jabs (but was only 3 days post-second when I got covid) and my covid was mostly pretty mild, altho worst (and bad enough to cal in sick which I otherwise never do) on days 8 and 9.

www.nationalacademies.org/based-on-science/can-a-covid-19-test-tell-me-if-im-contagious

Some useful info here. Basically PCR tests detect coronavirus DNA, LFTs detect coronavirus proteins. How contagious you are depends on the amount of active coronavirus particles in your body - neither of these tests are designed to look for active viral particles.

Quarantine periods have been determined by research studies using clinical trials in infected patients and PCR testing. And also (probably) trying to culture active virus from patients at various points post-recovery.

Basically what you’re asking though is whether a LFT would provide evidence that you weren’t contagious. The answer to that is no. Internationally, isolation periods vary from 7days to 14days - and we’re certainly not alone in opting for 10 days (Spain, Italy, US).

Sorry, see the thread has moved on from when I started writing! You’re not meant to test for 90days post COVID as there could be coronavirus proteins (for LFTs) or DNA (for PCR) still hanging around despite the virus no longer being active and no longer able to be transmitted and cause infection in someone else. So the thing about not testing is basically just because it’s pointless - could lead to positive tests which could spark needless isolation and contact tracing and muck up data analysis!

The guidance has definitely been contradictory on the non use of LFTs for 90 days I agree. I work as a nurse in care home sector though and we were advised ( following some backwards and forwards on it) that we should suspend LFT testing as well as PCR testing for any staff member for90 days post a positive covid result due to the potential risk of false positives getting thrown up.