Clinical context should be considered when ordering, interpreting troponin test

Guidance on when to order and how to interpret a troponin level, in order to initiate appropriate treatment and to optimize outcomes, was offered last week by a new consensus document issued by six medical societies.

Elevated troponin levels by themselves do not indicate myocardial infarction (MI, defined as myonecrosis due to ischemia), the document states. Troponin levels are nonspecific relative to the etiology of cardiac myonecrosis and occur in many nonischemic clinical conditions. As assays become more sensitive, more conditions that elevate troponin by even small amounts will be identified, the document continues.

The consensus document was developed in collaboration with the American College of Cardiology, American Association for Clinical Chemistry, American College of Chest Physicians, American College of Emergency Physicians, American Heart Association, and Society for Cardiovascular Angiography and Interventions.

The full report appeared online at the American College of Cardiology website and will be published in the Dec. 12 Journal of the American College of Cardiology.

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% over six to nine hours 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. Two exceptions include Food and Drug Administration-approved troponin testing for prognosis in CKD patients and treating chemotherapy patients who have a drug-induced cardiac injury.

The consensus document also defines the prognostic significance of an elevated troponin level 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.