Troponin I: an update on clinical utility and method standardization.

Cardiac troponin I (cTnI) is now widely recognized as one of the preeminent biochemical markers for the diagnosis of myocardial injury. The biochemical specificity of this biomolecule for cardiac tissue has forced a reevaluation of the diagnostic criteria for non-Q-wave acute myocardial infarction, unstable angina, acute coronary artery disease, and minor myocardial injury. Further, its use by clinicians has revolutionized the way that chronic and acute heart diseases are both diagnosed and managed. Unfortunately, the standardization of cardiac troponin I assays is problematic. Up to 20-fold variation of serum cTnI mass determinations may be observed for a given patient sample when measured by different assay systems. As a result, significant ambiguity often exists in the clinical interpretation of serum cTnI concentrations. Recent efforts have been directed toward the biochemical standardization of cTnI assays. However, the heterogeneous nature and biochemical complexity of the serum forms of cTnI and differences of the epitope recognition by the various methods have hindered the harmonization of serum cTnI assays.