The National Institute for Health and Care Excellence (NICE) from the UK has just published new recommendations for the use of high sensitivity troponin to rule out NSTEMI in the Emergency Department. You can find it at this link. I was honoured to be part of the team looking at this, as a specialist advisor. Here are some of my thoughts on what NICE says and the implications for our practice.
[DDET The Bottom Line]
You may just want to know the bottom line. If so, here it is..
You can rule out NSTEMI if you use a high sensitivity assay (Roche troponin T or Abbott ARCHITECT high sensitivity troponin I) providing that the levels are normal (below the 99th percentile) on arrival and 3 hours later.
If that’s all you wanted to know, you can stop right there. It’s that simple! If you want to know a bit more about what that actually means, and if you want to understand the important caveats, keep reading and, of course, check out our podcast (which gives even more information) at the end!
[DDET Does this guideline tell me what to do with patients who have chest pain?]
No. This isn’t a NICE clinical guideline. It’s simply a recommendation about how we can use certain diagnostic tests cost-effectively in the UK. That means the scope’s fairly narrow. The guidance only applies if your hospital uses one of two troponin assays:
- The Roche high sensitivity troponin T (cut-off 14ng/L)
- The Abbott high sensitivity troponin I (cut-off 26ng/L)
It’s also about ruling out (not ruling in) NSTEMI early on. Because it’s a UK guideline and we have the 4-hour ED target, NICE considered that an ‘early rule out’ strategy would be one that gets patients home within 4 hours of arrival.
[DDET Caveat 1: What if my hospital uses another troponin assay?]
There are lots of other troponin assays out there. When NICE looked at the characteristics of each assay, only two could reasonably be classed as ‘high sensitivity’. The others can still be used in practice but these recommendations don’t apply. If you want to follow what NICE says and you’re using those assays, you still need to run tests at 10-12 hours from symptom onset because looking at the evidence for those assays just wasn’t part of this project.
You should also bear in mind that NICE didn’t look at anything other than troponin – so this guidance doesn’t cover things like copeptin or H-FABP. It doesn’t cover the new decision rules like MACS, HEART, the ADAPT protocol or the ED-ACS score.
[DDET Caveat 2: What about unstable angina?]
These recommendations are about ruling out NSTEMI. That’s right – it means that unstable angina hasn’t been considered. Troponin can’t help you to diagnose unstable angina because patients with that diagnosis have, by definition, no rise and/or fall of troponin. This means that you still need to do some thinking. Not everyone who has normal troponin levels at 3 hours can go home. If the patients are high risk, you should still be admitting them to hospital. You could leave this up to the clinical judgement of the treating doctor, but a better idea might be to use some kind of formal risk stratification – whether that be the TIMI score, Goldman score, etc.
[DDET Caveat 3: How will this work with the 4-hour target in the UK?]
If you work in the UK, you’ll know that your patients need to have decisions made at an early stage about whether they can be discharged or need to be admitted. If you fail on this mission, you may face a fate worse than death. If you do a 3-hour troponin, that means the patient has the test before their 4 hours is up. But there’s a big challenge for us here…
The first blood test is unlikely to be taken at exactly time zero (when the patient first sets foot in the ED). It might be taken half an hour later, realistically. The second test should then be taken 3 hours later – so that’s now three and a half hours after arrival. After you’ve taken the blood, the lab has to test it for you. That takes a minimum of an hour. (Still longer at many places in the UK) This means that your patient has been waiting for longer than 4 hours – and you’ll therefore still need to admit them to hospital.
So, ultimately, these recommendations might not stop us from having to admit patients to hospital – but they will at least reduce the length of stay.
[DDET What’s the evidence for these recommendations?]
Ah, now you’re asking the best question of them all. NICE ran a systematic review and an economic analysis for these recommendations – but it’s not in the public domain just yet. When it’s published, I’ll let y’all know the full details including all the juicy gossip. Keep posted!
You can catch our podcast right here!
If you’re implementing these recommendations, we recommend that you audit what you’re doing. There’s a tool to help with this on the NICE website. You can find it here. If you are running an audit, please get in touch. We really should pool our efforts!
Until next time,