Variability of High-Sensitivity Troponin T Concentrations in Emergency SettingsImpact for the Diagnosis of Myocardial Infarction

Objectives: To assess biological variation of troponin T in emergency settings and establish limits for interpretation of serial results. Methods: We studied 6,557 consecutive patients with troponin measurements. A stable reference subset was selected to estimate biological variation and threshold limits. Results: The first troponin level was elevated in 32% of patients, and 2,490 had a second troponin level with a myocardial infarction (MI) prevalence of 16.2%. In the stable reference group with at least one abnormal value, the 99th percentile of the absolute delta between the first two samples was 16 ng/L. For MI diagnosis, the area under the receiver operating characteristic curve was 0.85 (confidence interval [CI], 0.83-0.87) for the first troponin level and 0.94 (CI, 0.93-0.95) for the absolute delta. Conclusions: An absolute delta of 16 ng/L has good specificity in the emergency setting. This threshold is valid for any sex, age, and sampling interval between 3 and 24 hours and is higher than published limits found in healthy outpatients.