A study was undertaken to evaluate the clinical relevance of serum troponin T (TnT) as a marker of ischemic myocardial injury, using a new automated enzyme immunoassay. The reference range for serum TnT was established by measuring serum TnT concentrations in blood obtained from 262 healthy subjects. The serum concentration of TnT was compared to serum creatine kinase activity, creatine kinase MB (mass and activity), myoglobin concentration, and lactate dehydrogenase activity: in 77 patients with myocardial infarction (55 received thrombolytic treatment); in 32 patients with unstable angina; in 30 patients with nonischemic heart diseases; and in 40 patients with skeletal muscle injuries. Our findings showed that: a) 99% of healthy blood donors had TnT concentrations0.10 micrograms/L; b) the test had a high clinical efficiency in the diagnosis of acute myocardial infarction, with a sensitivity of 1.0 and a specificity of 0.88 at a decision level of 0.20 micrograms/L; c) serum TnT had a later peak value (8-38 h), but a wider diagnostic window (126 h) than the traditional markers considered in the study; d) serum TnT had an excellent sensitivity in the detection of microinfarctions in patients with unstable angina pectoris; e) the release patterns of serum TnT were qualitatively different in perfused versus nonperfused patients. Peak serum TnT values and time to peak values were statistically different (p = 0.0336 and p = 0.0001) in reperfused and nonreperfused AMI patients, respectively; f) a ratio of serum TnT at 16 h to serum TnT at 32 h after chest pain1 provided a good indication of reperfusion in thrombolytic treatment (94% efficiency).
