Editor’s Choice-Rule-in of acute myocardial infarction: Focus on troponin

It is important to establish the diagnosis of acute myocardial infarction (AMI) expeditiously so that an immediate treatment plan can be developed. However, rapidly diagnosing AMI is challenging because patients with possible AMI constitute a heterogeneous group. Many of these patients will have increased cardiac troponin (cTn) levels in the absence of AMI, especially with high-sensitivity cardiac troponin (hs-cTn) assays.1,2 Furthermore, although chest pain represents the most common presenting symptom, up to 40% of patients with non-ST segment elevation AMI present with dyspnoea or other non-specific symptoms.3 The term ‘high-sensitivity’ reflects the assay’s characteristics and two criteria have been proposed to define an hs-cTn assay: (a) the total imprecision at the 99th percentile should be ≤10% and (b) measurable concentrations above the assay’s limit of detection and below the 99th percentile should be attainable for at least 50% of healthy people.4 Novel rule-in strategies have recently been developed based on the use of hs-cTn assays and taking advantage of their increased analytical sensitivity and precision. The aim of this review is to provide a condensed summary of the key characteristics and performance measures of these strategies, including some important limitations, so physicians can select and apply the strategy that best suits their local needs.