Expert Consensus Document Offers Advice On Troponin Tests Reply

A newly published document provides practical advice on the use of the popular and potent troponin tests. The Expert Consensus Document on Practical Clinical Considerations in the Interpretation of Troponin Elevations was developed by the American College of Cardiology Foundation in collaboration with several other societies to help address the many complex issues raised by the introduction of the tests in clinical practice.

Sanjay Kaul, a co-author of the document, said the document does not contain new information, but was written to respond to the request of clinicians “for help regarding the considerations for ordering, interpreting, and using troponin as a decision aid in the management of patients with ACS and non-ACS conditions.” The document provides “a roadmap for the proper use of troponin in the setting of appropriate clinical context. The hope is to avoid unnecessary testing and referral as well as inappropriate utilization of downstream diagnostic and therapeutic interventions.”

The document helps physicians understand when they should order troponin tests and how to interpret the results. The recommendations are designed to work in coordination with the recently updated universal definition of MI, and provide detailed information about the use of troponins in acute coronary syndromes, PCI, CABG, and a variety of nonischemic clinical conditions.

“There are many things that can cause damage to the heart muscle that would allow troponin to leak in the circulation where we can measure it, and it’s not always due to heart attack,” said L. Kristin Newby, the co-chair of the writing committee, in an ACC press release. “So 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.”

“We need to be thinking about why we are ordering the troponin test before we order it,” said Newby. “We hope this document provides a road map to help clinicians be more deliberate when ordering these tests and interpreting the results.”
Click here to read the ACC press release…

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New Universal Definition Of MI Unveiled At ESC 2012 1

A new universal definition of myocardial infarction (MI) was unveiled today at the European Society of Cardiology meeting in Munich. The document was developed jointly by the European Society of Cardiology (ESC), the American College of Cardiology (ACC), the American Heart Association (AHA) and the World Heart Federation (WHF) and will be published in five journals: the European Heart Journal, the Journal of the American College of CardiologyCirculationGlobal Heart and Nature Reviews Cardiology. (The document  was scheduled to go online on Sunday but is now available, along with extensive support material, on the American Heart Association website.)

The third universal definition of MI establishes the troponin levels required to make a diagnosis of MI in various situations. In a press release, Kristian Thygesen, the co-chair of the document task force, discussed the difficulties the task force encountered in reaching a consensus. Setting a troponin level for procedure-related MIs is difficult “because interventional cardiologists and surgeons do not want myocardial infarction as a complication,” he said. “It means that they want to set the levels of troponin as high as possible. It was also difficult to reach a consensus because it’s impossible to conduct a clinical trial to find the answer.”

The Task Force also expects the new definition will be adopted by the FDA and will be used in clinical trial protocols accepted by the FDA. Said Thygesen, “this is significant because it will help to standardize the way myocardial infarction is defined in clinical trials, making comparisons between trials more meaningful. Steering committees that write protocols for clinical trials do follow FDA requirements.”

Here is a summary of the new definition from a FAQ published by the AHA:

The preferred biomarker overall and for each specific category of MI is cardiac troponin (cTn) (I or T), which has high myocardial tissue specificity as well as high clinical sensitivity. An increased cTn concentration is defined as a value exceeding the 99th percentile of a normal reference population (upper reference limit, URL).

Myocardial infarction is determined by the specified cTn value, and at least one of the five following diagnostic criteria:

  1. Symptoms of ischemia
  2. New (or presumably new) significant ST/T wave changes or LBBB
  3. Development of pathological Q waves on ECG
  4. Imaging evidence of new loss of viable myocardium or regional wall motion abnormality
  5. Identification of intracoronary thrombus by angiography or autopsy

Troponin Test May Allow Rapid MI Rule-Out in the Emergency Department Reply

More than three-quarters of people with chest pain can be triaged within an hour of arrival at the emergency department with a novel strategy utilizing high-sensitivity cardiac troponin (hs-cTnT), according to a study from Switzerland published in the Archives of Internal Medicine. The strategy is promising, according to anaccompanying editorial, but much work remains before it can be implemented in clinical practice.

Tobias Reichlin and colleagues first studied 436 patients and developed a treatment algorithm utilizing hs-cTnT baseline changes and absolute changes over the initial hour. The algorithm was then tested in a second validation cohort of 436 patients, with the following results:

  • 60% were classified as “rule-out”
  • 17% were classified as “rule-in”
  • 23% required further observation
  • Overall sensitivity and negative predictive value: 100% for rule-out
  • Specificity for rule-in: 97%
  • Positive predictive value for rule-in: 84%
  • Prevalence of MI in the observational group:  8%
  • 30-day survival: 99.8% in the rule-out group, 98.6% in the observational group, and 95.3% in the rule-in group

The authors claim that their strategy “may obviate the need for prolonged monitoring and serial blood sampling in 3 of 4 patients.”

In an accompanying comment, L. Kristin Newby writes that the Swiss study “is a major advance in understanding the application of hsTn testing that with continued development could substantially improve evaluation of ED patients with suspected MI.” However, she notes that the excellent results obtained in this initial study will probably not be equalled in the real world. In addition, she writes, “although touted as ‘simple’ by the authors, the need for multicomponent algorithms that are different for rule-in and rule-out and that vary by age group or other parameters will challenge application by busy clinicians unlikely to remember or accurately process the proposed algorithm. As such, it will be imperative that hsTn algorithms, if validated, are built into clinical decision support layered onto electronic health records so that testing results are provided electronically to physicians along with the algorithmic interpretation to allow systematic application in triage and treatment.”
Click here to read the press release from Archives…