Cardiac troponin T and cardiac troponin I: relative values ... - CiteSeerX

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Robert M. Califf,2 Christopher B. Granger,2 Steven Peck,2 Karen S. Pieper,2. Paul W. Armstrong,3 Hugo A. ... collected within 3.5 h of ischemic symptoms for predicting ...... Antman EM, Tanasijevic MJ, Thompson B, Schactman M, McCabe.
Clinical Chemistry 44:3 494 –501 (1998)

Enzymes and Protein Markers

Cardiac troponin T and cardiac troponin I: relative values in short-term risk stratification of patients with acute coronary syndromes Robert H. Christenson,1* Show-Hong Duh,1 L. Kristin Newby,2 E. Magnus Ohman,2 Robert M. Califf,2 Christopher B. Granger,2 Steven Peck,2 Karen S. Pieper,2 Paul W. Armstrong,3 Hugo A. Katus,4 and Eric J. Topol5 for the GUSTO-IIa Investigators

acute coronary syndromes, from unstable angina to acute myocardial infarction (MI), has been an active area of research [1– 6].6 These investigations have been driven, in part, because biochemical markers are minimally invasive and clinical indicators such as the frequency, timing, and duration of ischemic symptoms, along with the electrocardiogram (ECG), can often differentiate unstable angina from acute MI [7, 8], but these indicators are not useful in stratifying patients in the short term. A further role for biochemical markers may be as a guide for intervention. Although no appropriate trials addressing these issues have been completed to date, Lindahl et al. reported that cardiac troponin T (cTnT) identifies unstable coronary artery disease patients who benefited from long-term treatment with antithrombotic therapy [9]. Troponin T and troponin I function together as essential components of the contractile apparatus in striated muscle [10]. Although the troponin complex functions similarly in all striated muscle, isoforms of both troponin T and troponin I differ in cardiac vs skeletal muscle because these proteins are coded by separate genes in these tissues [11]. Both the myocardial and skeletal isoforms of troponins T and I show striking differences that include biological function, amino acid sequences, and molecular weight. Further, the proportion of total troponins T and I representing the “cytosolic pool” available for rapid release and time of increase after myocardial necrosis differ [12, 13]. Therefore, the characteristics of these proteins may differ with regard to risk stratification.

We compared cardiac troponins T (cTnT) and I (cTnI) collected within 3.5 h of ischemic symptoms for predicting clinical outcomes in 770 patients. cTnT (cutoff >0.1 mg/L) and cTnI (cutoff >1.5 mg/L) were concordant (both positive or negative) in 90.4% of patients. Among discordant results, 66 were cTnT positive and cTnI negative vs 8 who showed the reverse (P