ESC's Ultra-Short MI Rule-Out Algorithm May Not be Sharp Enough: Analysis

Larry Hand

October 21, 2016

CHRISTCHURCH, NEW ZEALAND — The European Society of Cardiology (ESC) 2015 guideline 0/1-hour algorithm to rule out/rule in acute MI may be useful in identifying patients who need expedited care, but it falls short of emergency-department physicians' safety goal of at least 99% sensitivity, according to new research[1].

Dr John W Pickering (Christchurch Hospital Emergency Department, New Zealand) and colleagues used two high-sensitivity troponin assays to assess troponin levels in patients presenting in emergency departments with chest pain. They assessed for possible acute coronary syndrome (ACS) at hospitals in New Zealand, Australia, and Canada.

The current report, published online October 17, 2016 in Circulation, is a secondary analysis that combines data from five studies with a total of 2222 patients (mean age 59.7 years, 53.3% male).

Pickering and colleagues measured patient levels of troponin using the high-sensitivity troponin I (hs-cTnI, Abbott Diagnostics) assay and the high-sensitivity troponin T (hs-cTnT, Roche Diagnostics) assay and then compared their sensitivity and specificity for ruling out or in for AMI using the ESC guidelines algorithm.

Overall, for the hs-cTnI assay, the algorithm ruled out 1205 (54.2%) with a sensitivity of 98.8% and ruled in 310 (14.0%) with a positive predictive value (PPV) of 68.1%. For the hs-cTnT assay, the algorithm ruled out 1425 (64.1%) with a sensitivity of 97.1% and ruled in 292 (13.1%) with a PPV of 63.4%.

"The ESC 0/1 hour algorithm applied with hs-cTnT had lower sensitivity than expected from the preceding research that led to the guidelines," the researchers wrote. "Neither algorithm exceeded 99% sensitivity, a safety level which most emergency-department physicians consider required."

Dr Allan S Jaffe (Mayo Clinic, Rochester, MN), coauthor of an accompanying commentary[2], told heartwire from Medscape in a phone interview that the results weren't surprising. He also pointed out that high-sensitivity troponin assays in this study are used "everywhere except in the United States," because the Food and Drug Administration has not approved them for use.

"There are some gaps in that algorithm that needed to be considered and that hadn't been and need to be repaired," he said.

"Most of the validation studies, including the study just published, don't have a very substantial number of patients who present early after the onset of symptoms. From the point of view of the rule-out arm, if you present late, or reasonably late, the likelihood of overlapping with the criteria that are involved is quite small. But if you present early before troponin is apt to be released in substantial quantities, it is that group that is at risk," he said.

"One needs to be cognizant of the fact that the validation isn't as robust in regard to the early presenters as I would like to see it be. And unfortunately, the study that is published didn't have a lot of early presenters either," he said.

He presented three other issues regarding the algorithm in his commentary.

  • With development of the criteria for the algorithm having been done with the troponin T assay, it disadvantaged the troponin I assay. "Intrinsically, whenever you use one assay as a gold standard you disadvantage the other," he said.

  • The validation studies evaluated patients with chest pain, the cohort the algorithm was developed for, but they missed patients who might have MI without chest pain. "We shouldn't give these people the impression that we're diagnosing myocardial infarction. What we're diagnosing is myocardial injury, and some proportion of that is myocardial infarction," he said.

  • Missing from the literature all along has been information on follow-up and whether it is needed for the algorithm to be used successfully.

In his commentary, he gave six elements that could improve the outlook, including superimposing the use of an electrocardiograph to improve the rule-out approach, additional trials in all-comer emergency-department patients, and a randomized trial according to 1-hour rule-out or standard 3-hour rule-out.

The study had no specific funding and Pickering reported no relevant financial relationships. Disclosures for the coauthors are listed in the article. Jaffe reported consulting for most major diagnostic companies, including Roche, Abbott, and Siemens. Disclosures for the coeditorialist are listed in the article.

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