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New high-sensitivity troponin (hs-Tn) assays can detect minute amounts of troponin, potentially allowing earlier definitive diagnosis of acute myocardial infarction (AMI) than is currently possible (JW Emerg Med Apr 16 2010). In a prospective observational international study, researchers compared the diagnostic accuracy of absolute and relative changes in troponin I and T levels measured with hs-Tn assays in 1197 consecutive patients who presented to emergency departments with symptoms suggesting AMI and without ST-segment elevation on the initial electrocardiogram. Usual care was provided. The final diagnosis of AMI was determined by independent cardiologists who were blinded to the hs-Tn assay results.
Blood samples drawn at presentation and at 1, 2, 3, and 6 hours were available for 590 patients. AMI was the final diagnosis in 108 patients (13%). Absolute changes in troponin levels performed significantly better than relative changes on all performance measures. The absolute change in troponin T within 2 hours had a sensitivity of 89%, specificity of 93%, positive predictive value of 64%, and negative predictive value of 98% for AMI; results were similar for troponin I. Absolute changes at 6 hours (available for 305 patients) did not improve on the accuracy of those at 2 hours.
Reichlin T et al. Utility of absolute and relative changes in cardiac troponin concentrations in the early diagnosis of acute myocardial infarction. Circulation 2011 Jul 12; 124:136.
Comment
This was a study of chemical measurements, not of clinical care, which proceeded in the usual fashion; thus, the findings should not change practice. The study does, however, offer the prospect of changes to guidelines, which could speed throughput and allow more rapid determination of the need for interventional cardiology measures.