Background: 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.
Methods: 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 microg/L for troponin T levels might be more useful in risk stratification. A prospective validation of two cutoff levels (0.03 microg/L and 0.01 microg/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.
Results: Patients with troponin T levels >0.1 microg/L had greater 30-day mortality (5.5% [201/3679]) than did those with levels <or=0.1 microg/L (2.2% [75/3436], P <0.001). A cutoff value of 0.03 microg/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 microg/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.
Conclusion: Using a cutoff of <or=0.01 microg/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.