Developed in collaboration with other leading professional societies, the document is the first comprehensive consensus document outlining clinical considerations for ordering and interpreting tests for troponin. Since troponin testing was first introduced in the early 1990s, it has predominantly been used and defined in the context of diagnosing or ruling out myocardial infarctions (MIs). However, although a positive troponin test is an accurate indicator of injury to the heart muscle, it is not specific to MI, and may be a red flag for other illness or problems. The new expert consensus document aims to address this issue and provides a framework for clinicians to interpret the results of troponin testing "in a useful mechanism-based construct."
Specifically, the document recommends that physicians adopt the recently updated definition of MI 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. Further, the document gives recommendations for troponins in acute coronary syndromes (ACS), in non-ACS ischemic troponin elevations, in percutaneous coronary intervention and coronary artery bypass grafting, in nonischemic clinical conditions, and in other nonischemic conditions in which interpretation creates clinical uncertainty.
In addition to providing a review of the most recent research on troponin testing and its clinical application, the document also defines an elevated troponin level as a "sensitive and specific indication of cardiac myonecrosis, with troponin release from myocytes into the systemic circulation." In addition, the document notes, "in and of itself, elevated troponin does not indicate MI (myonecrosis due to ischemia); rather, it is nonspecific relative to the etiology of cardiac myonecrosis." Further, "troponin elevation occurs in many nonischemic clinical conditions, and as assays become more sensitive, more conditions that results in low-level troponin elevations will be identified."
The document also explains when a troponin level should be obtained:
- Because it is not specific for MI, troponin evaluation should be performed only if clinically indicated for suspected MI.
- An elevated troponin level must always be interpreted in the context of the clinical presentation and pre-test likelihood that it represents MI.
- Troponin is recommended for diagnosis of MI in chronic kidney disease (CKD) patients with symptoms of MI (regardless of severity of renal impairment). Dynamic changes in troponin values of ≥20 percent over six to nine hour should be used to define acute MI in end-stage renal disease patients.
- In the absence of specific interventions based on the results, routine troponin testing is not recommended for nonischemic clinical conditions except: U.S. Food and Drug Administration-approved troponin testing for prognosis in CKG patients; and treatment of patients undergoing chemotherapy who have drug-induced cardiac injury.
It also defines what the prognostic significance of an elevated troponin level is and provides at-a-glance resources for physicians, including a schematic of potential reasons for elevated troponin levels and flow diagrams to help clinicians determine when to use troponin in therapeutic decision making.
"We need to be thinking about why we are ordering the troponin test before we order it," said Kristin Newby, MD, MHS, FACC, co-chair of the writing committee. "We hope this document provides a road map to help clinicians be more deliberate when ordering these tests and interpreting the results."
However, the document authors caution that troponin levels should not be used in isolation or as a routine screening test in the emergency department or other settings. "As troponin assays become increasingly sensitive, understanding the clinical scenario will become increasingly important in deciding who to test, and integration of clinical data along with laboratory data will become even more crucial to the diagnosis resulting from testing," they note.
The document was developed in collaboration with the American Association for Clinical Chemistry, American Association of Chest Physicians, American College of Emergency Physicians, American Heart Association, and Society for Cardiovascular Angiography and Interventions.