Jon Deeks FMedSci Profile picture
Sep 22, 2020 10 tweets 3 min read Read on X
BMJ Editorial @bmj_latest on why Moonshot is scientifically unsound.

with Tony Brookes and @AllysonPollock

has just been published here

bmj.com/cgi/content/fu…

#Moonshot @UoB_IAHR @unibirm_MDS

1/10
Moonshot plans uses point of care tests (POCT) approved for home use which don’t yet exist.

Proposals use computer modelling not empirical evidence. Understanding model assumptions is critical.

Widely claimed model is based on using LESS ACCURATE TESTS. This is WRONG.

2/10
The model assumes new POCT is positive in people who have INFECTIOUS Covid-19

and negative in both those who don’t have COVID-19 infection at all

and negative in those who have NON-INFECTIOUS Covid-19.

(infectious means you can pass the virus to somebody else).

3/10
So the Moonshot POCT tests need to be very sensitive for INFECTIOUS Covid-19

but don't need to be sensitive for Covid-19 INFECTION.

So they still need to be very accurate tests, but for a different target condition. It’s a subtle but really important point.

4/10
And it is definitely not an opportunity for any duff test with lower sensitivity to enter the market.

But many seem to be taking the opportunity to try.

5/10
It is easy to make this test in a computer model, but real life is much harder.

We don't have hard and fast ways of knowing whether somebody is infectious or not. Our only tool is viral culture, which is hard to run and has high failure rates - so no reference standard.

6/10
PCR cycle threshold (Ct) value is a proxy measure of viral load known to correlate with viral culture. But as culture is unreliable & Ct values vary between runs, machines and labs, we can't set a safe threshold for Ct to distinguish between infectious and non-infectious.

7/10
So we don’t have the POCT tests we need for Moonshot,

and even if we did,

we don’t have an way to validate that they reliably identify all cases that are infectious.

If they miss infectious cases they will allow the virus to continue to spread.

8/10
Initially people just exposed and infected have low viral loads. PCR can pick them up before they are infectious and appropriately isolate.

Moonshot POCT test will pick them up only when they are infectious. Tests must be used frequently to minimise numbers they infect.

9/10
Specificity? No harms were considered in the model.

With specificity>99% ten million tests a day generates thousands of false positive results, causing unnecessary legally enforced isolation of cases and contacts with consequences for economy and for civil liberties.

10/10

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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
Jul 7, 2021
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
Read 11 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

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