Circulation. 2021 Jun 25. doi: 10.1161/CIRCULATIONAHA.121.054302. Online ahead of print.
ABSTRACT
Background: Whilst the 99th percentile is the recommended diagnostic threshold for myocardial infarction, some guidelines also advocate the use of higher troponin thresholds to rule-in myocardial infarction at presentation. It is unclear whether the magnitude or change in troponin concentration can differentiate causes of myocardial injury and infarction in practice. Methods: In a secondary analysis of a multi-centre randomized controlled trial, we identified 46,092 consecutive patients presenting with suspected acute coronary syndrome without ST-segment elevation myocardial infarction. High-sensitivity cardiac troponin I concentrations at presentation and on serial testing were compared between patients with myocardial injury and infarction. The positive predictive value (PPV) and specificity were determined at the sex-specific 99th percentile upper reference limit (URL), and rule-in thresholds of 64 ng/L and 5-fold of the URL for a diagnosis of type 1 myocardial infarction. Results: Troponin was above the 99th percentile in 8,188 (18%) patients. The diagnosis was type 1 or type 2 myocardial infarction in 50% and 14%, and acute or chronic myocardial injury in 20% and 16%, respectively. Troponin concentrations were similar at presentation in type 1 (median [25th percentile - 75th percentile] 91 [30-493] ng/L) and type 2 (50 [22-147] ng/L) myocardial infarction, and in acute (50 [26-134] ng/L) and chronic (51 [31-130] ng/L) myocardial injury. The 99th percentile and rule-in thresholds of 64 ng/L and 5-fold URL gave a PPV of 57% (95% confidence interval [CI] 56-58%), 59% (58-61%) and 62% (60-64%), and a specificity of 96% (96-96%), 96% (96-96%) and 98% (97-98%), respectively. The absolute, relative and rate of change in troponin concentration was highest in patients with type 1 myocardial infarction (P<0.001 for all). Discrimination improved when troponin concentration and change in troponin were combined compared to troponin concentration at presentation alone (area under curve, 0.661 [0.642-0.680] versus 0.613 [0.594-0.633]). Conclusions: Although we observed important differences in the kinetics, cardiac troponin concentrations at presentation are insufficient to distinguish type 1 myocardial infarction from other causes of myocardial injury or infarction in practice and should not guide management decisions in isolation. Clinical Trial Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT01852123.
PMID:34167318 | DOI:10.1161/CIRCULATIONAHA.121.054302