A War on Two Fronts: Battling Both False Positive and False Negative Chest Pain Evaluations
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My talk at the University of Maryland Emergency Cardiology Symposium #UMECS16 How to get your chest pain evaluation right, avoiding both false positive and false negatives. Learn how to use symptoms, the physical examination, risk factors and your gestalt or clinical judgement in accordance with the best evidence. You can catch the full recording of the talk FREE here - http://livestream.com/UMEmergencyMed/events/4813792/videos/117744022
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A War on Two Fronts: Battling Both False Positive and False Negative Chest Pain Evaluations
- 15. NO RISK FACTORS DOES NOT MEAN NO ACS 12 24 19 14 21 0 1 2 3 4 or 5 %withAMI Number of risk factors B o d y e t a l , R e s u s c i t a t i o n 2 0 0 8 ; 7 9 ( 1 ) : 4 1 - 5
- 16. But we're all great diagnosticians! Sure, sure. I M A G E B Y N E L S O N S A N T O S , H T T P : / / U P L O A D . W I K I M E D I A . O R G / W I K I P E D I A / C O M M O N S / C / C 8 / D R . _ H O U S E _ C A R I C A T U R E . J P G
- 18. C L I N I C I A N G E S T A L T 9 5 16 36 53 0 15 30 45 60 Def not Prob not Could be Prob is Def is %withMACE "Is this ACS?" B o d y e t a l e m e r g m e d j 2 0 1 4
Editor's Notes
- The problem is that this is actually very difficult, even in experienced hands. We've done lots of research to show that the nature of a patient's symptoms is a very poor predictor of whether the diagnosis is ACS in this undifferentiated group. What you can see here is a summary of some research from Martin's group in the Asia-Pacific region - a multimeter study from, I think, 12 centres in 9 countries. In that study, which I was privileged to collaborate on, patients' symptoms were coded as typical for ACS, atypical or a combination of the two. We found that patients whose symptoms were completely atypical were just as likely to have ACS as those patients whose symptoms were completely typical. So we can't rely on a patient's symptoms. If a patient has symptoms that can't be explained and ACS is even a possibility, then we need to investigate.
- Rick Edd Carlton in the south of England ran a terrific study called TRUST, and he’s just published an analysis – with Louise – in which he showed that atypical symptoms have just 51% sensitivity for AMI. So the good news is that typicality of symptoms seemed to have a 1% advantage over tossing a coin. The bad news is that 49% of patients with an acute myocardial infarction have atypical symptoms.
- Now here's another thing that we often do very badly. I know that none of you would ever consider discharging a patient with chest pain just because they don't have any risk factors, but we do tend to place a lot of importance of the number of risk factors a patient has for ischaemic heart disease. If they have no risk factors, we feel a little bit reassured. If they have all 5, we feel worried. There's probably a good reason why we feel worried - we know that patients with risk factors are more likely to have IHD, so when they present with chest pain we rightly think that it could be an AMI. But what this study shows, again from our group in Manchester, is that the number of risk factors a patient has really doesn't seem to make any difference to the probability of AMI. Again, this is probably more of an emotional thing than a rational one. I suspect that some patients are being investigated for ACS simply because they have 4 or 5 risk factors, although clinically they really don't have ACS - they have something else. There's also an element of patient behaviour in there too - if you know you're at high risk of heart disease you're more likely to come in with any little twinge of chest pain than if you're previously completely healthy and never worried about your heart. I think the take home message is that we shouldn't ignore risk factors, but we certainly shouldn't place too much emphasis on them. What's much more important is what's going on right now. Don't let the past history interfere with that because it's what's going on right now that you need to deal with.
- Amal Mattu quote about gastritis. So we have to be cautious with chest pain
- So maybe this ought to be about cost. We don’t have a bottomless pit of money in any health service. Admitting everyone and running every investigation would run up huge costs, which would be unsustainable. Maybe what we need isn’t necessarily the cheapest option but the most cost-effective. In the UK, we have the National Institute for Health and Care Excellence or NICE, which issues guidance on what constitutes cost-effective healthcare for our National Health Service. NICE has a ceiling for what it considers cost-effective care. It says that, in the UK, we should be willing to pay up to £30,000 (or $50,000) to gain one additional quality adjusted life year through healthcare. So that’s one year in full health as opposed to being dead. If we have to pay more than that to gain a quality adjusted life year, then that healthcare is not considered to be cost-effective and won’t be recommended.
- In Sheffield, Steve Goodacre has done some excellent work modelling the financial costs. And he found that, compared to running just a single troponin test on arrival in the ED and discharging patients based on that, we’d have to pay over £88,000 to gain one extra QALY by running another troponin sample after 10 to 12 hours. That’s three times NICE’s ceiling of £30,000! The one troponin test on arrival isn’t high sensitivity – it’s a standard troponin, and we all know how that isn’t very sensitive. But what drives this lack of cost-effectiveness is that we admit so many patients who don’t have ACS. Clearly, as clinicians we want a more accurate test than a single troponin sample taken on arrival – but these data show us just how pressing that need is. We’re burning money! Now, as purist clinicians we might not feel so passionate about financial cost being the primary driver of our care rather than patient outcomes. So maybe we are more interested in the more patient-related outcomes. But there is a human cost to over-investigation as well.
- Missed ACS: how big a problem is it? Old studies: Collinson – 7%. Pope 2%. Higher mortality with missed AMI
- False positive troponins; false positive CTCA
- Balance: who decides what’s right? Policy makers? For sure. Patients? Ideally. Chest Pain Choice
- The bottom line