The development and use of biochemical markers of cardiac damage is in a dynamic state. Creatine kinase (CK), aspartate aminotransferase (AST) and creatine kinase muscle± brain (CK±MB) remain in widespread use, but cardiac-speci®c isoforms of troponin T (cTnT) and troponin I (cTnI) have emerged as sensitive and speci®c indicators of myocardial infarction which are also used for risk strati®cation of patients with acute coronary syndrome. The diagnostic performance of the troponins has been widely evaluated. It is important, however, that other factors, such as analytical performance, interpretation of results, availability out of hours and in vitro stability are considered before any new test is brought into routine use. Most laboratories store routine samples for up to 14 days at 48C. Retrospective analysis of cardiac markers is occasionally requested if the diagnosis of myocardial injury is not initially apparent or if the clinical presentation changes. Published and manufacturers’ data on long-term in vitro stability of cardiac markers are limited. This study examines the stability of ®ve cardiac markers, CK, AST, CK±MB, cTnT and cTnI at 48C over 14 days.
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