High-Sensitivity Cardiac Troponin T for Early Prediction of Evolving Non-ST-Segment Elevation Myocardial Infarction in Patients with Suspected Acute Coronary Syndrome and Negative Troponin Results on Admission

BACKGROUND: We sought to determine the diagnostic performance of the new high-sensitivity cardiac troponin T (hs-cTnT) assay for early detection of non-ST-segment myocardial infarction (NSTEMI) in patients with acute coronary syndrome. METHODS: We enrolled patients with retrospectively confirmed unstable angina or NSTEMI and an initially negative cTnT concentration and compared the performance of baseline concentrations and serial changes in concentration within 3 and 6 h. Percentage change criteria included >= 20% delta change and ROC-optimized value. RESULTS: Based on the standard fourth-generation cTnT result of >= 0.03 mu g/L, an evolving NSTEMI was diagnosed in 26 patients, and 31 patients were classified as having unstable angina. With the use of the hs-cTnT assay at the 99th-percentile cutoff, the percentage of NSTEMI cases detected increased gradually from 61.5% on presentation to 100% within 6 h, and the overall number of MI diagnoses increased by 34.6% (35 vs 26 cases). A delta change >= 20% or >= ROC-optimized value of >117% within 3 h or >= 243% within 6 h yielded a specificity of 100% at sensitivities between 69% and 76%. The standard cTnT at the 99th percentile was less sensitive than hs-cTnT for early diagnosis of MI on presentation, and follow-up samples obtained within the initial 3 h demonstrated very low specificity of cTnT compared with hs-cTnT. CONCLUSIONS: The high-sensitivity cTnT assay increases the number of NSTEMI diagnoses and enables earlier detection of evolving NSTEMI. A doubling of the hs-cTnT concentration within 3 h in the presence of a second concentration >= 99th percentile is associated with a positive predictive value of 100% and a negative predictive value of 88%. (C) 2010 American Association for Clinical Chemistry