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Cardiac troponin is the preferred biomarker for defining the acute coronary syndrome and acute myocardial infarction. Currently, the only decision limit formally endorsed with regard to the cardiac troponins is the 99th percentile. This is a "rule-in" criterion, intended to ensure that only persons with the acute coronary syndrome are reviewed. The 99th percentile is an arbitrary cut point and there are many problems associated with its application, including defining a truly healthy population, the difficulty of standardisation of cardiac troponin assays, especially but not only cardiac troponin I, and the effects of age and sex on this parameter. The Emergency Department (ED) screens many more persons for possible acute coronary syndromes than actually have the condition and their needs are best met by a "rule-out" test that enables them to clear their busy departments of the many persons who do not actually have the condition. The needs of the ED are not optimally met using the 99th percentile. The index of individuality for the cardiac troponins is small and significant changes consistent with an acute coronary syndrome can occur without the 99th percentile being exceeded. It appears that the ED may be better served by use of delta troponin changes rather than the 99th percentile, but there are problems with this approach, particularly in persons who present late when troponin release has plateaued. In addition, there are many non-acute coronary syndrome causes for cardiac troponin release. The needs of the cardiologist and the ED physician are so different that it may be inappropriate for both groups to use the same diagnostic criteria for cardiac troponin, and it is of great importance that cardiac troponin measurement be used as only one part of the assessment of the person presenting with possible acute coronary syndrome.

Background: The management of patients presenting with symptoms suggestive of acute coronary syndrome is a significant challenge for clinicians. Guidelines for the diagnosis of acute myocardial infarction require a rise and/or fall of cardiac troponin, along with other criteria. Knowing what constitutes a significant delta change from baseline is still unclear and the literature is varied. Methods: We compared three methods for determining cardiac troponin delta changes (relative, absolute and z-scores) for detecting acute myocardial infarction in 806 patients presenting to an emergency department with symptoms suggestive of acute coronary syndrome. Blood specimens were collected at admission and 2, 3, 4 and 6 h postadmission and tested on the Roche Elecsys high-sensitivity troponin T assay. Results: A positive diagnosis for acute myocardial infarction was found in 39 (4.8%) patients. ROC AUC showed better performance for the absolute and z-score delta change (0.959–0.988 and 0.956–0.988, respectively) compared with relative delta change (0.921–0.960) at all time points in the diagnosis of acute myocardial infarction. Optimal timing for the second sample was at 4–6 h postadmission. Conclusions: Although not statistically significant, the results show a trend of absolute and z-score delta change performing better than relative delta change for the diagnosis of acute myocardial infarction. The z-score approach allows for a single cut-off value across multiple high-sensitivity assays which could be useful in the clinical setting. Our study also highlighted the importance of interpreting cardiac troponin changes in the clinical context with a combination of the patient's clinical history and electrocardiogram. [ABSTRACT FROM AUTHOR]