First High-Sensitivity Troponin Assay Finally Comes to the United States

US physicians who’ve been waiting to get their hands on high-sensitivity troponin tests don’t have to wait any longer. Last week, the US Food and Drug Administration (FDA) gave 510(k) clearance to the fifth-generation Elecsys Troponin T STAT assay (Roche), the first high-sensitivity or “new generation” troponin assay approved for use in the United States.

This test, and similar high-sensitivity assays, have been used for several years in most other parts of the world to help in diagnosing patients with suspected MI. It’s unclear why approval has taken so long in the United States, but some US experts have expressed concerns about the possibility of excessive testing or difficulties in sorting through piles of additional information with the availability of high-sensitivity assays.

Nevertheless, the news will be greeted with enthusiasm by those who have eagerly awaited the tests’ arrival this side of the Atlantic.

James Januzzi Jr, MD (Massachusetts General Hospital, Boston), told TCTMD in an email that the approval of this assay “is of considerable importance.”

“We test troponins in thousands of patients on a daily basis, and make significant treatment decisions on the basis of the results,” he said. “Chest discomfort is one of the most common diagnoses we see in the emergency department setting, and having a more sensitive test to identify or exclude acute myocardial infarction is a big step forward.”

Studies performed outside the United States have generally demonstrated that incorporating the results of high-sensitivity troponin tests speeds the triage of patients with suspected ACS, although a recent Australian study failed to show major changes in clinical management or outcomes when a high-sensitivity troponin T assay was used.

Januzzi said that these newer assays overcome some of the limitations of traditional tests.

“One of the biggest weaknesses of conventional troponin methods in the setting of acute myocardial infarction is the fact such assays are frequently negative at first draw and require hours before they become abnormal,” he explained. “Highly sensitive troponins provide substantial advantages over conventional troponin assays in that they allow for more rapid detection of cardiomyocyte necrosis and at an earlier time point.”

High-sensitivity assays are also able to rule out acute MI at the first blood draw if the values are very low and are accompanied by other reassuring clinical characteristics, he said. “So, it will totally change how we evaluate patients for MI.”

‘Devil Is in the Details’

Allan Jaffe, MD (Mayo Clinic, Rochester, MN), agreed that the availability of this new assay will have a beneficial impact on practice, noting that high-sensitivity assays are helpful both in evaluating patients with chest pain and with triaging patients who may be at risk for other cardiovascular morbidities that do not involve ischemic heart disease.

But he pointed out that the specific details regarding how the FDA will allow the assay to be used have not yet been released. The agency and Roche did not immediately respond to TCTMD requests about those specifications.

“The devil is in the details from that point of view, because the values that you need to do some of these things are sometimes very low values,” Jaff said. “And it is not at all clear, at least it wasn’t at the time several of us visited the FDA, that the FDA was amenable to allowing all results to be reported.”

Without knowing what the FDA will permit, it remains unclear whether the European experience with the assay will be directly applicable to US practice, he said, adding. “There are a lot of issues related to implementation where the details will be terribly important.”

That said, “this is a better assay for troponin T,” Jaffe stated. “There will be benefits either way. The question is the magnitude of the benefits."

And, Januzzi added, now that the first high-sensitivity assay has been cleared in the United States, more will soon follow.

“Thus, it’s important that every institution sits down now to discuss how they will implement these important assays,” he said, pointing out that US physicians will be able to learn from the experience accumulated around the world. “I am confident that while there’ll be a learning curve, the transition will not be as difficult as some may fear.”