Posted by: Tony Copperfield29 August 2012
Yeah, sure, I know you don’t come here expecting clinical education and debate. No – you come here anticipating reactionary views, cynicism, bile and swearing. Lots of swearing.
But look. There I was reading the hot-off-the-press NICE Guidance on venous thromboembolism. As you do, you know? Except that you don’t, obviously. Not normally. But I did. I did it so you don’t have to. Just view it as an enhanced Copperfield service.
And as I was reading, I experienced such an increasing sense of incredulity that I thought the guidance deserved a wider audience.
It highlights and encourages the use of the Wells score. (Bear with me, it gets better.) The Wells score, as you may or may not know, is a scoring system used to work out the likelihood of a deep vein thrombosis (DVT). NICE says we should use it. But I’ve noticed that if we do, about two-thirds of the way through the process, something quite odd happens.
Let’s have a go:
1. If a DVT is suspected, you’re supposed to use the Wells score to estimate the clinical probability that you’re right.
2. Using this, you’ll end up with a score indicating DVT ‘likely’ or ‘unlikely’.
Don’t be distracted by the fact that, even if you score ‘unlikely’, NICE advises you to arrange a d-dimer blood test. Yes, that seems strange, and it’s difficult to arrange urgent d-dimers, manage the results and so on, but this isn’t the really weird bit (though it is pretty weird).
3. Let’s go back to the Wells score, which NICE is so keen on. I won’t bore you with the details of the system, but it’s predictable stuff about calf swelling, active cancer, immobility and so on in cases of – don’t forget this – suspected DVT.
This is where it starts going strange. Right at the end of the scoring system, you have this: ‘An alternative diagnosis is at least as likely as DVT.’ (Scores minus 2 – the most impactful criterion of the lot, in fact). Now, concentrate hard, it’s worth it.
If an alternative diagnosis is ‘at least as likely as DVT’, then I believe that makes a DVT unlikely – in which case, I’m not ‘suspecting’ a DVT (remember?) and therefore shouldn’t be using this scoring system at all.
And how can I estimate whether the alternative diagnosis is at least as likely as a DVT when I’m in the middle of a scoring system designed to estimate how likely a DVT is?
Do you see what has happened? Combine unthinking application of a scoring system that seems bizarrely flawed with a defensive approach to the result and you have anyone with even the suspicion of a whiff of a possibility of a DVT – anyone with a leg, in other words – ending up needing a d-dimer (and maybe more, I’ve spared you the detail).
And, lastly, here’s the really odd bit. If you go through it again and try to make sense of the whole thing, you end up disappearing up your own anus. You actually do. That’s where I am now. I am literally trapped in my own anus. It smells, it’s dark and it’s horrible, just like the future of medicine. Someone help me get the f**k out. There, you got what you wanted in the end.