2/n Study is here, as ever have a read. A very simple, nicely done RCT comparing the advice to wear masks with no such advice in Denmark:https://www.acpjournals.org/doi/10.7326/M20-6817 …
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13/n Ok, a technical addition that is nevertheless important. The authors do not report correcting their result for the test sensitivity and specificity of their serology test
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14/n Serology tests are used to find antibodies, and they are (as all tests are) imperfect So, usually we correct for the imperfections to get a better estimate of the true number of people with antibodies
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15/n In this case, the study found that 1.8% of people in the mask group had antibodies, compared to 2.1% of people in the non-mask group But those are just the RAW figurespic.twitter.com/NtiZuV9Uml
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16/n If we use the Rogen-Gladen estimator, which is a pretty standard correction for test characteristics, we see instead that 1.59% and 1.95% of people in masks/no masks were probably infected, respectivelypic.twitter.com/d4rPZ5kJVw
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17/n This sounds like a minor point, but it actually isn't - if only 1.59%/1.95% of people were infected, it means that the study was underpowered for its main analysis, and thus we can't conclude much from the results
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18/n Sorry, small correction - I used the final totals of 1.8% and 2.1% not the actual antibody numbers of 1.6% and 1.7% in that calculation. If you apply the correction properly, you get 1.56% masks and 2.09% non-masks
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19/n For some context, to find a difference this small, the study would've needed to recruit about 24,000 people, or 12,000 in each group, which is about 4x as big
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Not much of a lockdown if participants were 'adults spending more than 3 hours per day outside the home'
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Re. a general overview, when are SAGE going to change (downgrade?) their 'weak evidence of a small effect' summary of masks' putative benefits?
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@threadreaderapp pls unroll -
Hello, you can read it here:
@GidMK: So, The Big Mask study has been published, and I thought rather than expound on what the results DID show… https://threadreaderapp.com/thread/1329171522485772288.html … Enjoy :)
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