LAUSR

In this special issue of the journal there are 4 articles examining the value of high-sensitivity cardiac troponin (hs-cTn)4 cutoffs set below the conventional 99th percentile upper reference limit to rule out acute myocardial infarction (AMI) with a single blood test at the time of arrival in the emergency department. This strategy could obviate the need for serial blood sampling in a potentially substantial proportion of patients presenting with symptoms that are compatible with an acute coronary syndrome. The use of this method would also overcome one of the key limitations of cardiac troponin as a biomarker and could help to decrease overcrowding of hospitals and emergency departments, which is a growing problem internationally. The potential use of unconventionally low cutoffs may thus be one of the most clinically important advantages of hs-cTn assays. With the hs-cTnT assay (Roche Diagnostics Elecsys, 99th percentile 14 ng/L), this potential benefit was realized as early as 2011, and much of the existing evidence with this assay has focused on its use for ruling out a diagnosis of AMI. A single-center prospective study reported that, using the admission blood sample, the assay had 100% sensitivity for AMI when the cutoff was set at the limit of blank (3 ng/L) (1). Using this cutoff, 28% of patients could have had AMI immediately ruled out. A large retrospective study of 14636 patients later confirmed that a threshold of 5 ng/L [the limit of detection (LOD)] could also yield a very high negative predictive value (NPV) when applied to patients with no electrocardiogram (ECG) ischemia (2). Further studies have added weight to the suggestion that AMI can be considered ruled out in patients with an hs-cTnT <5 ng/L and no ECG ischemia. A prospective study of 463 patients showed that by use of this strategy 17% …