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Jon Deeks FMedSci

Follow @deeksj

23 Jul, 12 tweets, 4 min read

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 Not yet peer reviewed.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.

The difference in disease rates (computed by linking to test-and-trace data) was between a 25% reduction and a 22% increase.

The decision to adjust for background community rate was not pre-specified. If this is not done then the increase in infection could be as much as 55%.

The study was meant to PCR test all contacts in both arms - they failed to do this to most in the isolation arm - look at the difference here between n numbers for the PCR tests done. IT has failed to be able to compare asymptomatic spread

Test accuracy - this was the Orient Gene test which is 'meant' to be better than Innova. only 32 of 60 cases detected. In this scenario with recent exposure to an infected case there is real concern that those missed (who had lower viral loads) are or could become infectious.

The trial was underpowered to detect the differences it needed to- RCTs of tests are really difficult, and clearly this was a massive effort, but you can't get beyond the results not being conclusive.

It is seriously disappointing to see important data being misinterpreted by BBC against basic rules of statistics and study design. Why do we allow this?

It is really dangerous to interpret this study as showing this is a safe. For goodness sake, our kids have suffered enough

More comment is at the SMC
sciencemediacentre.org/expert-reactio…

Sorry - can see many are not understanding this. Let me put it more bluntly ...

In an RCT if one group gets to stay at home and the other group go to school, but at the end there is no statistically significant difference in the numbers at school, what the heck happened?

The bbc have now changed the article to deal with these criticisms - kudos to them.

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Jon Deeks FMedSci

@deeksj

18 Jul

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

Jon Deeks FMedSci

@deeksj

15 Jul

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

Jon Deeks FMedSci

@deeksj

7 Jul

@dhscgovuk

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

@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

Jon Deeks FMedSci

@deeksj

22 Jun

@dhscgov

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

Jon Deeks FMedSci

@deeksj

17 Jun

@educationgovuk

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

Jon Deeks FMedSci

@deeksj

17 Jun

@MHRAgovuk

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

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

Read 13 tweets

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