As the sensitivity of troponin testing improves, so must clinicians refine the way they order and interpret such tests, according to a new consensus statement issued by seven professional societies.
Clinicians have used troponin as a biomarker for myocardial infarction since the early 1990s. However, while an elevated level indicates myocardial necrosis, it does not necessarily mean that a myocardial infarction has occurred. There can be other myriad reasons for an increase in troponin.
The consensus statement – written by a 14-member group of experts – reviews the most recent research on troponin testing and its clinical applications. It also addresses frequently asked questions on what an elevated troponin level means, when the test should be ordered, and prognosis with a positive test. The statement also gives a schematic look at potential causes of a positive troponin test. The schematic is divided into ischemic and nonischemic causes, and then further broken down.
"We need to be thinking about why we are ordering the troponin test before we order it," said Dr. L. Kristin Newby, cochair of the writing committee for the ACCF 2012 Expert Consensus Document on Practical Clinical Considerations in the Interpretation of Troponin Elevations. "We hope this document provides a road map to help clinicians be more deliberate when ordering these tests and interpreting the results," said Dr. Newby, who is a professor of medicine in the division of cardiovascular medicine at Duke University Medical Center, Durham, N.C.
Troponin may be elevated because of heart failure, surgery, trauma, kidney disease, or pulmonary embolism, among other conditions. The biomarker may also show up in patients with sepsis or those taking certain chemotherapies, such as anthracyclines and cyclophosphamide, which are known to cause cardiac damage.
"If we are indiscriminate in how we order these tests or we aren’t paying attention to the clinical scenario before us, we may miss something important," said Dr. Newby.
Further complicating testing, the statement warns clinicians that "all troponin assays are not created equal," and that there "is a wide spectrum of assay quality in practice." The measurement of cardiac troponin is also not standardized, though there have been recommendations by the National Academy of Clinical Biochemistry on how to do so.
Most assays, however, are "able to selectively detect cardiac troponin to the exclusion of troponin from other tissues," according to the statement.
The statement also documents that elevated troponin deserves investigation because it is associated with worse outcomes.
"If you have a pulmonary embolism or end-stage renal disease and your troponin is elevated, your prognosis – how you are expected to do – is worse," said Dr. Newby.
According to the statement, for clinicians, the "best value of troponin testing remains in the diagnosis of MI." But even with that use, "it is important to understand the clinical context as treatment may vary considerably."
The 37-page statement was developed by the American College of Cardiology Foundation, the American Association for Clinical Chemistry, the American College of Chest Physicians, the American College of Emergency Physicians, the American College of Physicians, the American Heart Association, and the Society for Cardiovascular Angiography and Interventions.
The statement was published online (JACC 2012;60) and will also be available on the ACC’s website.