Jon Deeks FMedSci Profile picture
Jul 7, 2021 11 tweets 4 min read Read on X
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Includes unpublished studies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

Jul 23, 2021
Daily Testing in school study report is out but presentation by BBC here is SPIN SPIN SPIN

The trial failed to show convincing reductions in school absence, and could not rule out large increases in Covid transmission. Sensitivity of the test was 53%.

bbc.co.uk/news/health-57…
The preprint for this study is here. Not yet peer reviewed.

modmedmicro.nsms.ox.ac.uk/wp-content/upl…
BBC says that reduced absence by 33%, but the ITT analysis in the text says 20% reduction with 95% confidence interval from 46% reduction to a 19% increases (p=0.27). So no convincing evidence of a reduction.
Read 12 tweets
Jul 18, 2021
SO what’s this POSITIVE news about medical tests?

Said it would be Monday, but actually the news broke this afternoon. So an early release from my tease …

Thanks for sharing your hopes about what it might be … I enjoyed many of them … but none were that close.

1/10
For me, positive news would be knowing

1) High quality tests are developed using the best expertise from industry and universities

2)Tests are evaluated in strong robust studies to work out whether they work in the real world for the purposes to which they are put

2/10
3) Study findings report the truth about whether they do more good than harm, and not spun for profit, popularity or reputation

4) Tests are developed to meet the greatest public health needs

5) Tests are affordable and available in the populations that need them most

3/10
Read 11 tweets
Jul 15, 2021
This new study suggests LFTs in primary care have sensitivity of 95% and specificity of 89%, but it is FLAWED.

These results are misleading because of PARTIAL VERIFICATION BIAS

A quick lesson ….

1/9
sciencedirect.com/science/articl…
Participants were first tested with LFTs – 810 positive and 1736 negative. The investigators choose to test 217 of the 1736 negatives with PCR – that’s 1 in 8. This wasn’t a random sample as they were influenced by clinical characteristics as well as the test result.

2/9
The sensitivity / specificity calculation is based on all LFT+ves and 12.5% of LFT-ves as follows:

3/9
Read 9 tweets
Jun 22, 2021
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
Jun 17, 2021
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
Jun 17, 2021
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

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