There is a great deal of continuing debate raging over the use of “high sensitivity” troponins in the Emergency Department. But, it’s not the test alone at fault – the responsibility for interpreting and acting upon the results lay with clinicians. In the era of conventional troponins, the test was a powerful tool to rule-in myocardial infarction. With high sensitivity troponins, the greater value in the tool is in ruling-out.
However, while much is made of the theoretical beneficial test characteristics of high sensitivity troponins, few have measured actual patient-oriented outcomes. This group from Valencia, Spain, prospectively evaluated consecutive patients at a single institution as their laboratory switched from a conventional TnI assay to a highly sensitive one. Comparing 699 consecutive patients from the pre-hsTnI period to 673 consecutive patients in the post-hsTnI … there were too many baseline differences to draw any useful conclusions.
But, in an effort to salvage the paper, the authors perform a propensity-score matching algorithm to balance to cohorts. Based on these matched cohorts, for which they do not offer much in the way of detail, there were no differences in major adverse cardiac events or death at 6-month follow-up. Regarding management decisions after the change, they note patients were less likely to undergo non-invasive testing in a chest pain observation unit, but substantially more likely to undergo invasive procedures.
This is just a single-center experience, and their observations are incontrovertibly corrupted by the unfortunate change in patients characteristics across their study periods. It does, at least, provide some small window into how hsTnI might impact the management pathway for patients presenting with chest pain.
“High-sensitivity versus conventional troponin for management and prognosis assessment of patients with acute chest pain”
http://heart.bmj.com/content/early/2014/06/19/heartjnl-2013-305440.abstract
We have been using the high sensitive troponin assays in my ED for over the past couple of years. They certainly provoked quite a bit of angst when they first were introduced but we have gradually become accustomed to their use. I think the only possible benefit is in a more rapid rule out MI strategy although the guidelines have yet to really catch up with the science on this one.
But the lack of specificity has been a challenge. I certainly find myself ordering less troponins much in the same way that I would never order a d-dimer without substantial forethought. The 99% cut-off established by the manufacturer as abnormal was determined using 5000 healthy volunteers. Unfortunately we never order them in healthy volunteers so they are generally “positive” half the time. We often find ourselves repeating them in two hours (delta two hour) to look at a trend. Sometimes I wish we could go back to the old assays. I wonder if there are any ED’s who have done precisely this?
I agree that this paper does not really add very much to our thoughts on these high sensitive troponin assays. I think an interesting study would be to look at the negative effects of the drop in specificity, resource implications and potential over-diagnosis.
We've chattered a little bit about this on Twitter with Rich Body, Simon Carley, Louise Cullen, etc. … the test isn't so much a bad thing as is the lack of sophistication of the clinicians. Unfortunately, nothing seems so immovable than the momentum of clinical practice – and a "positive" troponin knee-jerk equals MI persistently, even at our academic teaching institution here.
The additive information is interesting – any detectable troponin conveys a poor prognosis – but not in the time frame of interest for Emergency Department evaluation.