This study states that 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.
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.
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.
Reference link- https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.121.054302
