• Unless you have new symptoms you aren't supposed to take an LFT for 90 days.

    Are you sure about that? That advice is true for PCR tests (assuming no new symptoms) but not for LFD as far as I can tell.

    PCR: https://www.gov.uk/get-coronavirus-test

    You should not use this service if you’ve received a positive PCR test result in the last 90 days, unless you get any new COVID-19 symptoms.

    I don't think there's any clear guidance on what to do if, for example, your 7th/10th day LFD test is still positive.

  • [Catching up]

    Thanks (and others who responded). It does seem a very mixed message around LFDs at the moment.

    My guess is that the "don't test with lateral flow within 90 days of positive PCR" advice is just a form of chinese whispers. It may have started with "don't test with PCR again within 90 days of positive PCR" (which is sensible), that was changed to "don't test within 90 days of positive PCR", and then a subsequent change moved the "test" to "test with lateral flow or PCR". Who knows. It may also have been political in that they were worried that testing care home workers, NHS staff or school staff within 90 days of a positive PCR might mean they had to isolate again, which they couldn't cope with en masse, and so they tweaked the guidelines to avoid that situation (even though latent lateral flow positives aren't anywhere near as common as latent PCR positives due to the vastly different sensitivity of the tests.)

    Just sent my daughter off to school (in full school uniform) solely to do a lateral flow test and then come home. I can see why they're doing them this way, it guarantees that it is being done (rather than parents saying they are doing them) and hopefully ensures it is being administered properly as it is witnessed (albeit by non-medical professionals). Also a bit odd as she had to do a lateral flow test at home before coming in, just for good measure, but I guess that will help identify any parents who claim they're doing the tests at home but aren't.

    Back on subject though, two of my daughter's friends (Y7 so 11/12 years old) had tested positive (by PCR) 3-4 weeks ago and initially they'd been told they didn't need to come in for these latest LFD tests today, but that changed a few days ago and they're all going in.

    It does make sense (to me at least). Irrespective of the politics and other limitations, if you're blowing positive on a LFD then there's a very good chance that you've got a high enough viral load for you to be actively infectious. Just because you first tested positive 10 days ago doesn't really change this. Allowing people to go out into the world when they are still blowing positive on an LFD 10 days later is quite bonkers in my opinion. If it had happened to my daughter (she stopped blowing positive on LFD 8 days after the confirmatory PCR and with 2 days of isolation left to go) I'd like to think we'd have continued to isolate at home for a few more days until we saw a negative LFD. (Obviously this gets trickier for people who, for whatever reason, continue to test positive for much longer than 10 days.) It was also easy for us to do as neither of us needed to go out of the house for any reason.

    Also remember that you'll hear the anecdata about odd test outcomes (people testing positive on one and negative on the other) much more often and much louder than all of the hundreds of thousands of tests that perform as expected each and every day. Between the three of us in our house we've had ~60 PCR tests and probably 100 LFD tests. The only positives were when my daughter was definitely infected, and we saw a pretty standard progression in LFD tests as that infection subsided. Unfortunately she missed the two subsequent PCR tests from the ONS so we've no idea if she would have tested positive on those once the LFDs had cleared up, she didn't test positive on PCR when she was next tested 12 weeks from the original infection. She also never got round to doing the ONS antibody test, and has now been jabbed.


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