Changes in Diagnosing Non-ST-Segment Elevation Myocardial Infarction after the Introduction of a New High-Sensitivity Cardiac Troponin T Assay: A Single-Centre Experience

Abstract

Cardiac troponins are the most sensitive and specific biochemical markers of myocardial injury and with the new high-sensitivity troponin methods very minor injuries of the heart muscle can be detected. The introduction of high-sensitivity assays has facilitated reference range adjustments and a revised cut-off point for myocardial infarction (MI) due to an improved performance in the lower concentration range. The objective of this study was to investigate whether implementing a high-sensitivity cardiac troponin T (hs-cTnT) assay with subsequent lowering of the cut-off point changed the hospital evaluation and diagnosis of acute non-ST-segment elevation myocardial infarction (NSTEMI) in a general hospital population. NSTEMI patients admitted to our hospital during two periods each lasting one year were retrospectively compared. During period 1 (August 2007 - July 2008) patients were diagnosed with a conventional troponin T assay, and during period 2 (August 2009 - July 2010) patients were diagnosed using an hs-cTnT assay. A significant increase in the number of NSTEMI admissions was observed using the hs-cTnT assay (225 vs. 341, risk ratio 1.57, 95% confidence interval 1.33 to 1.85). The proportion of patients examined with acute coronary angiography was similar (25.8% vs. 23.8%). Due to the higher number of NSTEMI admissions the total number of angiographies was higher in period 2 (58 vs. 81, p < 0.05), and significantly more patients were examined without signs of coronary artery disease (CAD) (0% vs. 8.6%, p < 0.05). A smaller proportion diagnosed with the high-sensitivity assay had significant dynamic cTnT changes between the highest and lowest cTnT measurement during each admission (96.2% vs. 88.7%, p < 0.01). More patients were diagnosed with NSTEMI and underwent coronary angiography after introducing the hs-cTnT assay. At the same time there was an increase in the frequency of coronary angiograms without signs of CAD, and fewer had significant dynamic cTnT concentration changes.