Even more data on LFTs out today.

@dhscgovuk released report of studies of Innova and Orient Gene, and their interpretation of findings.

Includes unpublished studies

BUT Clear evidence of post hoc interpretation of results based on naïve definition of infectiousness.

1/10
Long link is here:

gov.uk/government/pub…

2/10
@dhscgov define

HIGH viral load as >1,000,000 RNA/ml and appear to consider that these are the only cases which matter.

10,000 to 1,000,000 is LOW (not moderate)

<10,000 MINIMAL.

This is despite acknowledging there is no cut-off that categorises people as infectious

3/10
So policy is based on EXPERT OPINION ignoring EVIDENCE AND DATA.

There is absolutely no step change at Ct=18.3 (which is 1,000,000) in their graph of risk of secondary cases

This categorisation is a post hoc subgroup definition which makes the tests look falsely good.

4/10
All graphs in the report show sensitivity results in these three categories.

5/10
New studies include a University pilot in asymptomatic students (is this Durham University from last autumn? ) - test identified 5 of 17 cases sensitivity of 29%.

Liverpool, Birmingham and this study are now the only three in people without symptoms.

6/10
There are also 5 studies done at Regional test and trace centres in people with symptoms.

Including three with self-use testing (two or Innova, one of Orient Gene).

Some suggestion that sensitivity drops with self-testing for Innova by ~10%

7/10
But

STILL No studies of self-use in people without symptoms

STILL No studies of use in children at all.

8/10
There is a shocking amount of detail missing from these reports. Little attempt to report in line with the STARD reporting criteria.

There is no reason not to do this and it makes it very difficult to assess the risk of bias and applicability of these findings.

9/10
Key issue is equating viral load>1,000,000 as infectious and (more importantly) viral load <1,000,000 as not infectious.
Use of such a high threshold falsely makes tests look good.
Implying everybody else has “little infectious virus” is wrong and puts our health at risk.
10/10
Also of interest to note that the report cites Beale S as the source of the one in three people being asymptomatic.
The data from this review are below. Looks more like on in four than one in three. Can anybody explain?

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More from @deeksj

22 Jun
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
Read 7 tweets
17 Jun
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).

3/n

aic.mhra.gov.uk/era/pdr.nsf/na…
Read 11 tweets
17 Jun
IMPORTANT: MHRA New standards for LFT self tests for SARS-CoV-2 in people without symptoms.

@MHRAgovuk just published new Target Product Profile.

This is a guidance document based upon the best available evidence and independent expert opinion.

1/12

gov.uk/government/pub…
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 Image
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.

3/12 Image
Read 13 tweets
29 Apr
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
Read 5 tweets
28 Apr
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.
Read 5 tweets
17 Apr
For the sake of clear Public Health messages, listening to this interview on @theJeremyVine I'm tweeting some responses to the claims made by Peto

#1 "the lateral flow test has the remarkable ability of only picking up people who are likely to be infectious, or other words a danger to others."
It doesn't just pick out ONLY infectious people
It doesn't pick out ALL infectious people
Linkage to infectiousness is unclear.

It can only gives +ve results when viral loads are high (a limitation not an ability). Studies show viable virus in many people with low viral loads.
Read 19 tweets

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