Clinician’s Guide to Early Rule-Out Strategies With High-Sensitivity Cardiac Troponin
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Articles, see p 1586 and p 1597
Despite uneasiness among clinicians about the increasing sensitivity of assays for cardiac troponin (cTn), it is rare that clinical algorithms for laboratory-based tests have as much data to guide decision making as do high-sensitivity assays for cTn (hsTn) for diagnosis (rule-in) or exclusion (rule-out) of myocardial infarction (MI). Rather, the proliferation of research evaluating variations in such algorithms in the emergency department (ED) has the potential to overwhelm clinicians with options. In this issue of Circulation, 2 observational studies1,2 that directly compare the diagnostic performance of multiple hsTn-based testing strategies are a step forward in helping providers. These 2 studies illustrate several critical principles and tradeoffs driving the ongoing evolution of early rule-out strategies using hsTn. As a mandatory reminder, although the principles are informative, the specific algorithms discussed in this editorial are not applicable to the “contemporary sensitive”3 assays that predominate in current practice in the United States. In addition, the specific concentration values reported as cut points are for the hsTnI assay used in the 2 studies and will differ from the assay for hsTnT that has recently been approved in the United States.
Of the emerging applications for hsTn, the rapid rule-out of MI in the ED is the application most likely to be embraced by clinicians.4 This application most directly leverages the superior analytic and clinical sensitivity of hsTn assays as an advantage by translation into a robust negative predictive value (NPV) for MI. Consistent with the focus of the reports by Chapman et al1 and Boeddinghaus et al,2 this editorial addresses the negative predictive rather than positive predictive performance of these strategies and illustrates 3 major components of evolving early rule-out strategies with hsTn (Figure).