Use of High-Sensitivity Troponin Values in Suspected ACS Induces Few Changes in Practice

When treating patients with suspected ACS, making the results of a high-sensitivity troponin T (hs-TnT) assay available to physicians does not result in major changes in management or clinical outcomes, a randomized trial conducted in Australia suggests.

“The use of hs-TnT is supposed to be able to dichotomize patients into low and high risk more accurately and quickly,” lead author Derek Chew, MBBS (Flinders University, Adelaide, Australia), told TCTMD in an email. “To realize these benefits, [the assay] needs to be coupled with processes (protocols, decision rules) that more rapidly discharge low-risk patients and drive investigation of high-risk patients.”

James de Lemos, MD (UT Southwestern Medical Center, Dallas, TX), told TCTMD he was not surprised by the minimal impact seen with the reporting of hs-TnT results.

“It’s really kind of hard for me to believe that changing the troponin assay would do anything other than improve throughput and flow through the emergency room, that simply providing information from the blood test would actually lead to such marked changes that hard outcomes would be improved,” he said.

On the other hand, de Lemos added, “some of the good news is that they didn’t see a bunch of excess testing when the more sensitive assay information was provided.” That’s reassuring, he said, because he has been concerned that when high-sensitivity troponin assays are eventually rolled out in the United States—where they are not yet approved—the availability of such sensitive test results will lead to an “explosion of additional testing.”

Contributing to that fear is the greater use of troponin testing by US physicians compared with those in other parts of the world, driven both by a low threshold for testing and concerns about potential litigation stemming from missing MIs in the emergency room, de Lemos said.

“If [high-sensitivity assays] are not coupled with really careful algorithms to guide clinical decision-making, you’ll have a lot of unnecessary involvement of cardiologists in low-risk patients,” he said. “So it’s going to take a tremendous educational program when these assays are rolled out.”

Minimal Impact on Clinical Care, Outcomes

In the study, reported online August 9, 2016, ahead of print in Circulation: Cardiovascular Quality and Outcomes, investigators assessed the impact of troponin T testing reported at levels achievable with a high-sensitivity assay compared with testing reported at standard levels. For the high-sensitivity assay, hs-TnT ≤ 14 ng/L was considered normal and > 14 ng/L indicative of myocardial injury. For standard troponin testing, < 29 ng/L was considered normal, 30 to 100 ng/L deemed borderline abnormal, and > 100 ng/L indicative of myocardial injury.

The randomized study included 1,937 patients with chest pain or features of ACS who presented to five emergency departments in Adelaide between July 2011 and March 2013. All patients underwent troponin testing at presentation and at 3 and 6 hours unless discharged before then. The Elecsys Troponin T high sensitive assay (Roche Diagnostics) was used in all cases; only the reports provided to physicians differed between groups.

Provision of hs-TnT results did not affect numerous measures of clinical care, including admission rate, the proportion of patients discharged home directly from the emergency department, and subsequent use of invasive angiography, echocardiography, functional testing, or revascularization. In addition, physicians prescribed guideline-recommended medical therapies at similar rates in both groups.

The proportion of patients with a diagnosis of MI within the first 24 hours of admission did not differ between groups, although those assigned to hs-TnT reporting were more likely to have a final admission diagnosis involving a noncoronary cardiac condition.

In terms of outcomes, the composite rate of all-cause death or new/recurrent ACS within 1 year (primary endpoint) was not significantly lower in the hs-TnT reporting group (5.7% vs 7.1%; HR 0.83; 95% CI 0.57-1.22). Other clinical outcomes were comparable in the two arms, as well.

An analysis of the three-quarters of patients who had peak troponin levels below 30 ng/L within the first 24 hours, however, showed a reduction with hs-TnT reporting for the primary endpoint (2.6% vs 4.4%; HR 0.58; 95% CI 0.34-1.00) and all-cause death (1.0% vs 2.3%; HR 0.40; 95% CI 0.17-0.97).

“Given the limited impact on care, the modest reduction in recurrent cardiac events and mortality should be interpreted with caution, especially considering the multiple comparisons and the lack of difference seen for the primary outcome analysis,” the authors note. “Nevertheless, subtle differences in practice, particularly among patients with other noncoronary cardiac conditions, may account for differences in outcomes observed.”

‘Inertia of Clinical Decision-Making’

Chew and colleagues point out that European Society of Cardiology guidelines on the management of ACS call for the routine use of hs-TnT assays to be incorporated into care protocols.

“This study highlights the inertia of clinical decision-making in response to the adoption of new diagnostic and therapeutic innovations,” they note.

The minimal impact of reporting hs-TnT results might be explained by multiple factors, they say, “including a lack of clinical appreciation of the increased risk for future events associated with low-level elevations in troponin or the lack of mature decision-making and established investigative/management pathways for the care of patients with and without evidence of low-grade myocardial injury.”

They conclude that “for widespread use of hs-TnT testing in routine practice to be advocated, the incremental gains in clinical effectiveness of new [high-sensitivity] troponin-based protocols should be demonstrated within appropriately designed randomized clinical trials, as called for in international guidelines.”

 

 

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Source:Chew DP, Zeitz C, Worthley M, et al. Randomized comparison of high-sensitivity troponin reporting in undifferentiated chest pain assessment. Circ Cardiovasc Qual Outcomes. 2016;Epub ahead of print.

 

 

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