Societies offer guidance on troponin testing

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Physicians must consider the individual presentation and circumstances before ordering tropinin testing and evaluate the results in clinical context. That was the message of a consensus statement on troponin testing by the American College of Cardiology Foundation (ACCF) and a consortium of societies.

The document was published online Nov. 12 in the Journal of the American College of Cardiology.

The "ACCF 2012 Expert Consensus Document on Practical Clinical Considerations in the Interpretation of Troponin Assays" authors surveyed over two decades of experience with troponin, reviewed the results of clinical trials and suggested best practices for the use and analysis of troponin testing. L. Kristin Newby, MD, of Duke University Medical Center in Durham, N.C., and Robert L. Jesse, MD, of the Veterans Health Administration in Washington, D.C, both representing the ACC, were co-chairs of the writing committee.

Troponin is a protein that is indicative of injury to the heart muscle. When troponin assays became available in the 1990s, clinical experience demonstrated that elevated troponin levels were associated with increased risk of adverse outcomes. However, the test has come to be used as a tool to diagnose MI, a practice the consensus statement discouraged, in part because elevated troponin can arise from a number of other serious conditions.

According to the statement, "Elevated tropinin in and of itself does not indicate MI; rather, it is a sensitive and specific determinant of myocardial necrosis that is nonspecific relative to the etiology of that necrosis."

The statement considered the development of more sensitive troponin assays, making it possible to detect even low levels of troponin elevation. Noting that there are healthy members of the populace who will exhibit slightly elevated troponin levels, the authors urged clinicians to rely on both ECG and clinical indicators, as well as troponin levels, when diagnosing MI.

The statement emphasized that elevated tropinin indicates cardiac necrosis, not infarction. "Myocardial necrosis is a laboratory diagnosis that does not imply an etiology, whereas MI is a clinical diagnosis," according to the statement. Therefore, in the interests of patient care, it is critical that clinicians pinpoint the cause of the elevated troponin and develop an appropriate plan for treatment.

The statement also urged clinicians to recognize troponin's value as a prognosticator of poor outcomes, even when the troponin test does not reveal elevation significant enough to indicate MI. "It is incumbent on all practitioners to fully understand the implications of an elevated troponin level in a given patient in order to initiate the appropriate treatment and to optimize outcomes. This is extremely important, not only in distinguishing Type I from Type II MI, but also in distinguishing ischemic from non-ischemic causes," the authors wrote.   

The authors considered the best use and evaluation of troponin tests in Acute Coronary Syndromes (ACS), non-ACS ischemic conditions, coronary interventions (PCI and CABG) and non-ischemic clinical conditions. 

The American Association for Clinical Chemistry, American College of Chest Physicians, American College of Emergency Physicians, American Heart Association and the Society for Cardiovascular Angiography and Interventions also contributed to the document.