The sensitivity versus specificity trade-off

This issue of Heart and Metabolism is dedicated to the use of biomarkers in defining risk in acute coronary syndromes (ACS). Although superficially simple, I find this a complex topic dominated by the increasing sensitivity of the cardiac troponin (cTn) assays. The first task is to define ACS and risk. Evolving myocardial infarction (MI) is of most concern in a patient presenting with chest discomfort and a suspected ACS event. When the presenting electrocardiogram displays diagnostic criteria for STsegment elevation, biomarkers are irrelevant in guiding immediate management. Thus, the predominant use of biomarkers is in the triage of patients with a suspected ACS event, but without ST-segment elevation on presentation, so-called NSTE-ACS. Only about 10% of patients presenting with suspected NSTE-ACS end up with a diagnosis of acute myocardial infarction (AMI). This diagnosis is made using standard criteria based on a rise or a fall in a marker of myocardial necrosis, preferably troponin. The historical journey in AMI diagnosis is charted in the Refresher Corner article within this issue by Eggers. From this, it is clear why the troponins are now the favored markers to diagnose AMI among those presenting with suspected NSTE-ACS. However, as emphasized by Eggers, problems exist, leaving room for improvement.