Unlike CK-MB and myoglobin, the release of troponin I or T is specific to cardiac injury.
Troponin is released before CK-MB and appears in the blood as early as, if not earlier than, myoglobin after AMI. Approximately 30% of patients experiencing chest discomfort at rest with a normal CK-MB will be diagnosed with AMI when evaluated using troponins. Single-point troponin measurements equate to infarct size for the determination of the AMI severity. Accordingly, there is much support for relying solely on troponin and discontinuing the use of CK-MB and other markers.
Sources:
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Kavsak PA, MacRae AR, Newman AM, et al. Effects of contemporary troponin assay sensitivity on the utility of the early markers myoglobin and CKMB isoforms in evaluating patients with possible acute myocardial infarction. Clin Chim Acta 2007;380:213–6. PMID: 17306781.
Kontos MC, de Lemos JA, Ou FS, et al. Troponin positive, MB-negative patients with non-ST-elevation myocardial infarction: an undertreated but high-risk patient group: Results from the National Cardiovascular Data Registry Acute Coronary Treatment and Intervention Outcomes Network-Get With The Guidelines (NCDR ACTION-GWTG) Registry. Am Heart J 2010;160:819–25. PMID: 21095267.
Volz KA, McGillicuddy DC, Horowitz GL, et al. Creatine kinase-MB does not add additional benefit to a negative troponin in the evaluation of chest pain. Am J Emerg Med 2012;30:188–90. PMID: 21129891.
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