In November 2014, the National Institute for Health and Care Excellence (NICE) issued recommendations for the use of high-sensitivity cardiac troponin (hs-cTn) assays in the UK.1 Two assays were evaluated: the Elecsys hs-cTnT assay (Roche Diagnostics) and the ARCHITECT hs-cTnI assay (Abbott Laboratories). On the basis of both clinical and economic evidence, NICE recommended that hs-cTn assays could be used to ‘rule out’ the diagnosis of non-ST elevation myocardial infarction (NSTEMI) within 4 hours of patients arriving in an Emergency Department (ED). NICE further stated that this would typically involve ‘ruling out’ NSTEMI in patients with hs-cTn concentrations below the 99th percentile upper reference limit when tested both on arrival in the ED and 3 hours later. This recommendation was based on the findings of a commissioned systematic review.2 The systematic review had pooled existing evidence from 18 studies to define more granular ‘optimal’ testing strategies for each hs-cTn assay. However, diagnostic strategies based on such models may not perform as well when used in practice. Two Heart studies have made efficient use of existing data from large cohort studies to further evaluate the accuracy of those diagnostic strategies.3 ,4

Pickering et al3 pooled data from five cohort studies to examine the diagnostic accuracy of hs-cTn measured on arrival and 3 hours later, using standard cardiac troponin testing …