Assay-related issues in the measurement of cardiac troponins

The recently released document by the Global Task Force on the universal definition of myocardial infarction (MI) has strengthened the role of cardiac troponin increase as the main criterion for MI diagnosis. Despite this pivotal role in clinical decisions, a number of assay-related issues can still markedly affect the test performance in the everyday practice. Regarding imprecision and analytical sensitivity, the performance of commercial assays is variable. Moreover, at least for troponin I, there is a lack of standardization among assay results. Appropriate cut points (99th percentile limit of the reference value distribution and/or 10% CV concentration value) can be established only if the assay performance is known and taken into account. Key characteristics to be defined include characterization by appropriate experimental and statistical protocols of the assay detection limit, total imprecision, and definition of the 99th percentile limit of the reference population. The widespread introduction of cardiac troponin measurements is an undoubted improvement, but some performance differences still exist with commercial assays, which most clinicians are unaware of and may give rise to wrong marker interpretation.