Results from the LIVERPOOL EVENT PILOTS have been published on line and in the media. Somehow I missed these coming out. cultureliverpool.co.uk/event-research…
No official report from @dhscgov as per normal.
Seems important evidence is being delayed once again.
1/7
The bottom line is that the events were safe.
Kudos to Liverpool PH Team.
But detail is interesting to see why they were safe.
2/7
First the infection rate in Liverpool was very low when the events were held
Negative LFTs required for entry. 5/13263 positive and excluded. Same-day PCR found 4 people positive who had attended with false negative LFTs. So 5/9 were picked up by LFT – 44% missed.
3/7
7 more were PCR+ve a few days later- may have been infected at the event or elsewhere.
However less than half of those attending actually submitted PCR results, so likely to be a few other missed cases - that 5/9 might well be 5/13 or less - so 60% missed.
4/7
LFTs only stopped < half of those with Covid attending.
Safety of the event seems driven by (a) low prevalence of Covid at the time; (b) local PH team tracking and tracing cases and contacts; (c) intelligent local fst data management; (d) other mitigations at the venues.
5/7
This should NOT be taken as a “thumbs up” that LFT testing makes places safe.
These numbers are small, but show a “thumbs down” – performance is poor exactly as would be expected.
Seems like low prevalence and a good local Public Health team is what matters.
6/7
But it is really great that Liverpudlians could get out and have a good time safely.
What do we known about ORIENT GENE used in the Daily Contact Testing Trial by the @educationgovuk and @DHSCgovuk?
There have been claims that this test is as good as others and has been reviewed by @MHRAgovuk for use in assisted testing. This is not right
1/10
The process does not make sense.
The MHRA never review products for assisted testing as they are professional use tests, which go through the self-certification process to get a CE-IVD mark.
MHRA doesn't go near this process.
2/n
In fact ORIENT GENE is not even on the MHRA register of products which is a requirement. You can check here - both for the product and manufacturer (sorry for the messy link).
Important to note that the MHRA see these tests as for detecting “Current Infection”. That is detecting active infection, but is bigger than checking whether people are infectious. It also includes people who are pre-infectious.
2/12
They give guidance on reference standards to detect this. There are challenges here in establishing scientifically valid clinical reference standards. RT-PCR is regarded as acceptable which is what most are using.
The 1st 2 weeks of school testing did find MORE FALSE POSITIVES than TRUE POSITIVES - data are finally public.
Proportion false were 62% and 55% in these 2 weeks. Of 2304 positive tests, 1353 were likely false, with 1 positive per 6900 tests done.
Remember that the law made kids, teachers, families and bubbles had to isolate for 10 days even when the PCR came back negative, despite the @RoyalStatSoc spending days trying to explain the issues to @DHSCgovuk.
Never ever say tests don't do harm.
To be clear as some still can't see the problem. 2 weeks testing in every school only found 954 true cases. To find each one used 6884 tests (cost £144,564) and 1.4 false negatives were put into unnecessary isolation with bubble and family- 500 person days if a bubble affected 36
Well here is some real data from 27 health care workers who picked up symptomatic Covid-19 infections whilst being tested twice weekly using RT-PCR. The paper develops models to look at impact of testing frequency, but also hypotheses on LFT performance bmcmedicine.biomedcentral.com/articles/10.11…
There is excellent presentation of the original data in the paper, as well as results from the models. Kudos to the authors.
Plots of Ct values from PCR are provided, which show that RT-PCR with Ct<37 had a peak sensitivity for detecting infection of 77% 4 days after infection.
No LFTs were used in the study, but the paper considered test results with Ct<28 and Ct<25 as illustrations of how LFTs might perform. At Ct<28 the red spots are +ve LFT results, the black are -ve LFT results, peak sensitivity is 64% at 4.3 days post infection.
Ben Dyson, an executive director of strategy at the health department and one of Matt Hancock’s advisers, stressed the “fairly urgent need for decisions” on “the point at which we stop offering asymptomatic testing”.
“As of today, someone who gets a positive LFD result in (say) London has at best a 25% chance of it being a true positive, but if it is a self-reported test potentially as low as 10% (on an optimistic assumption about specificity) or as low as 2% (on a more pessimistic assumption