Anyway, in ideal conditions 71% of people who the watch said had AF actually had the condition Interesting, but largely unimportant A much more interesting figure is that, even in the best of conditions, 29% of people the watch said had AF probably didn't
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Without knowing the NPV, it's not possible to calculate the false positive rate, but given the information we have it's likely to be pretty high
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Health Nerd Retweeted Health Nerd
And coming back to the original tweet, that's a really big problem because the population prevalence of AF in people who wear Apple Watches is very lowhttps://twitter.com/GidMK/status/1107871498667094016?s=19 …
Health Nerd added,
Health NerdVerified account @GidMKThe reporting of this new Apple Watch study is not great - 0.5% rate of atrial fibrillation in the study (HUGE PROBLEM) - 34% positive predictive value in real-world conditions (rarely correct) - 71% PPV in ideal clinical conditions - watch mostly useless clinically https://twitter.com/CNBC/status/1107856005097054211 …Show this thread1 reply 0 retweets 5 likesShow this thread -
Without delving too far into the specifics, if you're screening large populations for a disease and only a few of them have it, your test has to be NEAR PERFECT Being wrong 29% of the time does not qualifypic.twitter.com/eluDH0aOBZ
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And on top of this all - something that NO ONE SEEMS TO MENTION ANYWHERE - is that AF screening >65 years is currently not recommended because we are unsure of the risks/benefits https://bjgp.org/content/67/660/296 …pic.twitter.com/q24z1MTL7o
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What about those <65 years? We haven't even looked at the question properly, because the population prevalence is so low that most epidemiologists agree it'd be a pointless waste of timepic.twitter.com/m6cOP1I9yC
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So on the one hand, we've got the Apple Watch study saying that the watch is pretty useless clinically On the other, we've got a dubious rationale for doing this in the first place and no demonstrated benefit And yet, the headlinespic.twitter.com/20e8PbkiLY
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(I'd like to point out that, in a wonderful twist, the Daily Mail has one of the best articles out on this all https://www.dailymail.co.uk/news/article-6816853/Apple-Watch-spot-heart-problem-research-needed.html …)
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Anyway, Apple is apparently doing a proper RCT looking at true clinical risk/benefit, so until those results are formally published and I can pick them apart I'm staying skeptical that this is anything interesting at all
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Replying to @GidMK
Have they registered it so we can see the protocol? Also: 1. If they use a similar population then why do an RCT when clinical utility is so poor and prevelance so low? Their going to need huge numbers too. 2. If they go w more prevalent group = need to demo clin utility FIRST
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Not registered as far as I know. And you're right, I should probably downgrade my hopes about any RCT to "hopefully not a useless trash fire" because yeh those are serious and problematic questions
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The press release refers to this paper for the study design https://www.sciencedirect.com/science/article/pii/S0002870318302710?via%3Dihub … which does suggest a registered trial: https://clinicaltrials.gov/ct2/show/NCT03335800 …
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Nah that's the registration for the study they just finished. The RCT is still a dream afaik
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