A third-generation troponin T assay with improved precision and a lower detection limit has been developed. However, the appropriate cutoff for identifying patients with the acute coronary syndrome who are at low risk of subsequent mortality has not been established.

A retrospective evaluation of data from the Fragmin and fast Revascularization during InStability in Coronary artery disease II (FRISC-II) trial suggested that a cutoff below 0.1 μg/L for troponin T levels might be more useful in risk stratification. A prospective validation of two cutoff levels (0.03 μg/L and 0.01 μg/L) was performed in 7115 patients with non–ST-elevation acute coronary syndrome from the Global Utilization of Strategies To open Occluded arteries IV (GUSTO-IV) trial.

Patients with troponin T levels >0.1 μg/L had greater 30-day mortality (5.5% [201/3679]) than did those with levels ≤0.1 μg/L (2.2% [75/3436], P <0.001). A cutoff value of 0.03 μg/L provided better discrimination between high and low risk: 5.1% (234/4552) versus 1.6% (42/2563). However, a cutoff value at the lower limit of detection, 0.01 μg/L, provided the best discrimination: 5.0% (254/5123) versus 1.1% (22/1992) (P<0.001). This cutoff level had the highest negative predictive value; it also discriminated best for the combined endpoint of death and myocardial infarction.

Using a cutoff of ≤0.01 μg/L for the third-generation troponin T assay, the detection level of the assay, is useful for identifying patients with the acute coronary syndrome who are at low risk of subsequent mortality.