The Gospel According to NICE- Chest Pain of Recent Onset: Assessment and Diagnosis. Updated Guideline 2016.

In November 2016, at a grand gala dinner at NICE HQ, the updated chest pain guidelines were released . The update was accompanied by fireworks, dancing girls and a clamour on social media. Emergency Departments were tearing up their current chest pain pathways and revising them according to the Gospel of NICE. Except there was no dinner, no fireworks, no dancing girls and barely a mention in the twitter-sphere. Is this because NICE missed a huge opportunity to improve care for patients presenting with acute chest pain?

The NICE chest pain guidelines are massively important to us. Up to 10% of patients we see have non-traumatic chest pain, not a shift goes by where we don’t place a patient on a chest pain rule out pathway. We look to NICE to guide us in developing these pathways. Many ED physicians take these guidelines as gospel, reading them at face value (well the summary at least-few of us have the time or inclination the read the full guidelines). As a self-confessed chest pain and troponin geek, I thought I would give you my verdict on the 2016 updated guidelines.

Let’s start with the positives:

You have to dig deep to find the new parts of this guideline (which is an update from 2010 rather than a revamp), which broadly focus on the use of high-sensitivity troponin assays. First we find the following statement: “Do not use high-sensitivity troponin tests for people in whom ACS is not suspected.” I think I know where NICE are going with this, i.e. do not just test high-sensitivity troponin in anyone who comes through the door, a welcome stance. Some may argue that high-sensitivity troponin may be useful in risk stratifying patients with pulmonary embolism or syncope but the jury is out here. Broadly speaking carefully selecting the patients which you chose to test high-sensitivity troponin in is an excellent approach, our recent podcast on this very topic is here.

The next statement that appeals is: “Ensure that patients understand that a detectable troponin on the first high-sensitivity test does not necessarily indicate that they have had a myocardial infarction.” High-sensitivity troponin tests have the ability to detect much lower levels of troponin. What NICE mean here is that some patients will have a detectable troponin, i.e. above the cut-off the laboratory use (called the 99^th percentile value), when they first come through the door but this does not necessarily mean they have had an MI. We need to do another test at 3 hours to see whether there is a rise or fall, and marry interpretation of this will the clinical presentation. For many patients this first abnormal test may be their “baseline troponin” and may be the result of other comorbidities such as age, hypertension, renal failure, COPD to name but a few. I think clinicians have got this concept, what NICE are trying to encourage is communicating this with patients. A welcome recommendation.

Being a clinical researcher, I am always interested to read the Recommendations for Research that are included at the end of all NICE guidelines, since the grant funders always take notice of these. Although I am disappointed that NICE have missed an opportunity to recommend further research to evaluate to clinical and cost effectiveness of the myriad of rule-out strategies out there (more on this in a bit), there is one recommendation that is very welcome: “How should information about the diagnostic pathway and the likely outcomes, risks and benefits, with and without treatment, be most effectively presented to patients” This is about bringing in the concept of “shared decision making” with our patients and how we can use it to improve the efficiency of rule out testing. We have seen this concept used to great effect in sudden onset headache/suspected subarachnoid haemorrhage; I don’t remember the last time a patient volunteered to have a lumbar puncture after a negative CT within 6 hours of symptom onset. We can potentially use it in the same way by presenting our patients with the risks, which are often negligible, of early discharge after high-sensitivity troponin testing. I would certainly welcome a trial that robustly tested this concept.

And now the negatives:

A big issue with the NICE guidelines is that they only refer to high-sensitivity troponin assays. Only two high-sensitivity troponin assays are currently approved by NICE. Roche high-sensitivity troponin T and Abbott high-sensitivity troponin I. Complexities with contracts with assay manufacturers mean that many labs use alternative assays, such as those made by Beckmann and Siemens. Many EDs use point-of-care troponin tests, since they feel it improves efficiency. It is vital that you know which assay your lab uses and understand that you cannot apply these NICE guidelines to your troponin assays (if you don’t use Roche or Abbott). This has huge implications since many units will be seen to be non-guideline compliant by commissioners (and medicolegal lawyers?!). Personally, I think this is a huge omission by NICE.

On the face of it, an exciting recommendation within these guidelines is that they give us a chance to discharge a patient using just a single high-sensitivity troponin test taken at presentation: “consider performing a single high-sensitivity troponin test only at presentation to rule out NSTEMI if the first troponin test is below the lower limit of detection.” The limit of detection for the Roche assay is <5ng/L and <2ng/L for Abbott. This represents a step change in practice. Having published a few papers looking at this concept, I agree that an undetectable high-sensitivity troponin taken at presentation has a very high diagnostic accuracy for ruling out NSTEMI. There are a few caveats here and I would urge caution:

1. Ruling out NSTEMI is not the same as ruling out ACS. The diagnostic accuracy may fall to unacceptable levels if we include patients who need revascularisation. I have seen patients who have had an undetectable troponin who have had a critical stenosis of a coronary artery needing urgent stenting. Picking these patients up is tricky but they key is in the history and risk factors, or that “gut feeling.” You wouldn’t want to be sending these patients home so good clinical assessment is vital.
2. There is some evidence that is early presenters (< 2 hours after chest pain) the diagnostic accuracy falls to unacceptable levels.
3. The clinical and cost effectiveness of using this strategy is unknown. How many patients can we really get home? Will they all return the next day or go and see their GP? Will it lead to increased downstream resource use? Is this approach acceptable to patients? These are key questions that NICE has failed to address.

NICE too have put in a caveat with the recommendation to use the limit of detection. They say this should be used only in patients who are “low risk using a validated tool.” This is where the guideline really falls down for me. They recommend the TIMI score or GRACE for this purpose. Neither score was designed for this use and no paper in the literature has combined either score with the limit of detection to report diagnostic accuracy. This recommendation seems to be plucked from thin air, which I find surprising, the bottom line is that we have no idea, at present, how this strategy will perform on the shop floor.

Part of the reason for including a recommendation that has no robust evidence to support it, is the sometimes obscure exclusion criteria NICE used in performing their literature review. It is striking to look down the reference list of the full guideline and see the absence of names such as Backus, Body, Cullen, Mueller and Than; key names in the advancement of chest pain evaluation in the ED. As a result, vast swathes of the literature are missing, including the HEART score (Backus), the T-MACS rule (Body), the ADAPT 2 hour pathway (Cullen), the 0/1hour testing strategy (Mueller) and the EDACS rule (Than). NICE will argue that assessing risk scores in-depth was outside of the remit of this update, I see it as a missed opportunity.

I would urge you to not blindly follow the Gospel According to NICE but to scout around the literature to find the best chest pain pathway that works for your ED. Whilst there are some positives to be gained from this guideline, for me NICE have missed an opportunity to improve patient care.

Edd Carlton

References

NICE- Chest Pain of Recent Onset: Assessment and Diagnosis. Updated Guideline 2016.

Backus: A prospective validation of the HEART score for chest pain patients at the emergency department. 

 

Body: Troponin–only Manchester Acute Coronary Syndromes (T-MACS) decision aid: single biomarker re-derivation and external validation in three cohorts.