Direct comparison of early elevations of cardiac troponin T and I in patients with clinical unstable angina

Background The aim of this study was to compare the prognostic efficacy of cardiac troponin T (cTnT) and I (cTnI) in patients with clinical unstable a ngina. Methods We studied 74 patients with chest pain at rest, electrocardiographi c evidence of myocardial ischemia, and normal (<6.7 ng/mL) values of creati ne kinase-MB. cTnT was measured with a commercial assay (cutoff level 0.1 n g/mL) and cTnI with a preliminary research application (cutoff level 3.1 ng /mL). All patients had blood drawn at baseline and 8 hours thereafter. The prospectively defined end point was the proportion of patients identified b y each assay as having myocardial damage. Results cTnT and cTnI were elevated in the same percentage of patients (18 of 74; 24%). Overall, 23 patients had elevations of 1 or both markers. In 1 3 there were elevations of both. Ten patients had elevations of only one (5 for each marker). In 51 patients, no elevations were present. Death or non fatal myocardial infarction was more frequent in patients with elevated cTn I (27.7% vs 5.3%; P = .02) than those with normal values. The prognostic in fluence of cTnT was less (17% vs 8.5%; P = .2). However, the difference bet ween the 2 markers when compared directly was not statistically significant (27.7% vs 17%; P = NS). Conclusions These data indicate that both markers identify myocardial damag e in equal numbers of patients with clinical unstable angina. Patients with elevations had a worse short-term outcome. The significance of the minor d ifferences in prognostic value will require additional studies.