Letter to the Editor
The headline and publication reviewed in the EMN article, “Hoopla Aside, hs-cTnI is Not Catching Missed MIs” are misleading. (2019;41:1; http://bit.ly/2Bv4FUd.) Rory Spiegel, MD, wrote, “Despite our hopes, it would appear that the introduction of hs-cTnI added very little to the workup of patients presenting with symptoms concerning for ACS.” On the contrary, a wide body of published research demonstrates that hs troponin can positively affect ED evaluation of ACS if properly implemented.
Our European and Asian colleagues have shown us for years that the value of a high-sensitivity troponin assay is not to identify more MIs but to identify patients who can be safely discharged home faster. Indeed, the literature is rife with examples of how this can be done. (Circulation 2017;135:e923; http://bit.ly/2tzs02Q; Eur Heart J 2016;37:3324; http://bit.ly/2NjMFAO.)
Our early experience at Duke University Hospital has confirmed this experience (manuscript in preparation). Thoughtful high-sensitivity troponin implementation strategies that incorporate structured risk stratification and disposition pathways significantly reduce length of ED stays, admission and stress testing rates, and costs without a concomitant increase in hard cardiovascular outcomes such as MI and death in those discharged. Note that these outcomes cannot be achieved simply by changing your troponin assay. They require an evidence-based, multidisciplinary change in the practice of ACS evaluation.
We agree that it is unfortunate that these assays have been termed high sensitivity because their real value is high precision and reproducibility. This allows for accurate serial measurements in a short time. They also allow more precise identification of extremely low (undetectable) levels that can allow safe discharge after one lab draw in select patients who present several hours after symptom onset.
Alexander T. Limkakeng Jr., MD
W. Frank Peacock, MD
Dr. Spiegel responds: Thanks to Drs. Smith and Limkakeng for their insightful comments. Both are well versed in their understanding of the literature surrounding the use of high-sensitivity troponins, and both argue that the results of Shah, et al., discussed in my EMN article are discordant from the remaining literature which demonstrates that high-sensitivity troponin assays can be used to safely discharge patients home from the ED without increasing the number of patients identified as positive for an acute myocardial infarction. They go on to cite a number of studies to support these claims.
While a number of studies have demonstrated that the introduction of a high-sensitivity assay allowed clinicians to send more patients home from the ED without increasing the number of patients diagnosed with AMI, an equal number have demonstrated the opposite. (Acad Emerg Med 2017;24:388; http://bit.ly/2Nuefvl; Heart 2014;100:1591; Emerg Med J 2012;29:805; Acad Emerg Med 2014;21:727; http://bit.ly/2IzUcg5.) Multiple studies have found that the use of high-sensitivity troponin is at best no better than the standard assay or at worst increases downstream testing.
In fact, all the studies that support the use of a high-sensitivity troponin are observational in nature. Their results are promising, but they are highly vulnerable to bias because of their observational design. The only other RCT I am aware of comparing the use of standard to high-sensitivity troponin assay found the high-sensitivity assay offered no clinical value over and above the standard assay. (Circ Cardiovasc Qual Outcomes 2016;9:542; http://bit.ly/2U7kHuR.) The results presented by Shah, et al., are even more concerning. They suggest not only that the assay is not beneficial, but also that it may lead to more downstream care with no recognizable benefit.
Both Drs. Smith and Limkakeng offer logical reasons why the Shah results do not represent the true value of a high-sensitivity assay, and they may be correct. Shah's results may be due to how the assay was deployed rather than the assay itself. But it is just as likely that the results are a representation of what will occur when high-sensitivity assays are introduced into the clinical arena. These results should not be written off because they are discordant from a sampling of observational data supporting the use of high-sensitivity assays. Rather, it is our responsibility to empirically demonstrate the clinical value of the high-sensitivity assay before welcoming its widespread use in EDs across the country.