Time to think about whether you are really an emergency medicine diagnostician…
Are you a diagnostician? Of course you are! Why do I even need to ask?
Well, to be honest I’m no longer very sure to be honest. When I speak to friends and colleagues in emergency medicine and ask them to describe themselves then ‘diagnostician’ is a word that is commonly used. Now I know what they mean and so do they, but is it the right word? Making a diagnosis is perhaps not quite as straightforward as you might think, and if diagnosis is quite as straightforward as we think then perhaps we are not diagnosticians.
[Ed – Eh? I’m getting lost in the semantics here – give us an example]
So, let’s think about something really easy. Have a look at the ECG below and tell me what the diagnosis is. The patient is a 54 year old man with chest pain.
So, I’ll bet that you said inferior MI didn’t you. You did, I know you did because I’ve had said the same thing too, but we would both be wrong, well possibly….
The first reason is that inferior MI is a politically incorrect diagnosis according to the politically correct guide to cardiology.
Secondly, and leaving the PC brigade behind, when we look at this ECG we come to a conclusion that it is indeed an MI but yet we also know that there are many ST elevation mimics such as LV aneurysm. In this case we know that we should still start therapy and get the patient off to cath lab but there is a possibility that we will be wrong (about 5% of the time in fact). So what we are doing is attaching a label (in this case MI) to a probability. So it’s probably an MI, so let’s treat it as an MI, and overall patients (as a population) will be better off.
Great, but that’s all a bit picky isn’t it? Does this really matter? Well in the example above perhaps not as we are going to treat on the basis of a high risk, so we have decided a diagnosis and we are going to treat. Now we know that this presents problems for some patients as the therapy for things like MI (and stroke) are risky in themselves so every so often we will harm a patient through a known complication of a therapy for a disease they do not have. Worth stopping and thinking about that one for a moment, it means that if we assign therapies on the basis of a probability harm will happen, sorry harm WILL happen.
The difficulties also arise when we consider what we might do in the exclusion of disease because the same problems arise. Let’s think of another example where we are seeking to exclude a diagnosis, if we are talkind about probabilities when ‘ruling in’ a diagnosis, then do we get similar problems when we ‘rule out’?
The diagnosis of the moment seems to be PE with loads of posts and debates pinging around the blogosphere, and I’m sure that you will seen a number of rule out strategies for the management of ?PE patients. I’ll also bet that in the majority of cases the implication of the rule out strategy is that if the patient is negative for investigation then the patient does not have a PE, but this is not true. Just as it’s not true for most rule out MI, appendicitis, UTI, renal stone, Sub arachnoid bleed protocols. What we are actually doing is moving patients from a pretest probability where we are worried down to one where the risks of pursuing further investigation outweigh the benefits. This is one of the reasons why I like the way Scott Weingart wrote the rule out PE pathway at EMCRIT. The one from Scott Weingart is not typical in that respect as the end point is ‘stop work up’ as opposed to PE ruled out – because it’s not. In reality the sensitivity of most PE rule out strategies is in the 90’s but they are certainly not 100%.
The obvious result of this is that if you use a typical rule out protocol you are really using a probability protocol and therefore you must be missing something. Let’s take a really good R/O protocol for PE that has 98% sensitivity, – that’s fab and 98% is regarded by most people as a SnOut, but what we now know is that a sensitivity of 98% means that we miss 2% of patients with disease. That’s 1 in 50 folks, with the implication that you will be missing a lot of serious disease in your career……or does it? (more of this later)
Now that you are worried that you’re not a diagnostician at all, just a doc playing the odds and gambling with your patients life it’s time to think about the implications of being a probablestician rather than a diagnostician, and perhaps why as clinicians we like more certainty than we typically justify. That’s for part 2.
PS. Since I made the word probablastician up I’m not sure how to spell it.
PPS. In future articles we will take about diagnosis and diagnosticians, but remember that things are rarely as certain as they seem.
For all posts in this series click here
Risky Business Part 7. Risk Proximity
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