LFTs and new variants

[Floxxy]

I have seen some rumours in the media that the current LFTs (UK) are not detecting some of the new covid variants. Has anyone else heard this and is it true?

[bennevisplace]

Media reports will be based on rumour rather than solid science, as the most recent systematic studies on lateral flow test (LFT), aka rapid antigen test (RAT) sensitivity were done long before current variants emerged. However, late last year concerns were already being expressed:

Recent research has found multiple commonly-used rapid antigen tests to now have diagnostic sensitivities below 30%, with sensitivities at or near 0% the first 48 hours of infection, using polymerase chain reaction (PCR) test positivity as the gold standard. Reliance on tests with low sensitivity could paradoxically increase transmission risk through false assurance.

ncbi.nlm.nih.gov/pmc/articl...

In the UK, we have moved from a situation where LFTs/RATs were largely selected and distributed by the NHS to retail distribution at market prices to individual customers without product knowledge. Product performance varies, in other words some makes of RAT are more sensitive than others and more likely to read positive when you are infected, see link.springer.com/article/1...

The risk of a false negative result has always been there with RATs, though, especially early in an infection, and in the absence of a PCR test it's good practice to do repeat RAT testing if you need to be sure - in fact that's official advice in the US fda.gov/medical-devices/saf...

[FairweatherSailor]

Interesting post. My wife and I spent a few days in Iceland in January (which was lovely) . On our return my wife immediately tested very solidly positive using an LFT. I was OK for 24 hours and then I started to feel unwell. I tested but could only make out a very faint line. I contacted 111 / CMDU and antivirals arrived quickly but I felt really dreadful , much worse than when I have had COVID before, and yet I only tested very faintly positive and in fact I started to test negative before I started to feel better. Took well over a week to recover from this variant. Not like the previous experience of COVID at all. Keith