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The European Society of Cardiology (ESC) 0/1-h algorithm using high-sensitivity cardiac troponin (hs-cTn) worked for triaging patients with suspected non-ST-segment elevation myocardial infarction (NSTEMI), according to one study.

Among patients presenting to the emergency department with suspected NSTEMI in 2006-2016 who had serial hs-cTnT measurements available for analysis (n=4,368), the ESC algorithm showed good safety for ruling out NSTEMI (negative predictive value [NPV] 99.8%) and accuracy of ruling it in (positive predictive value [PPV] 74.5%).

The overall efficacy of this algorithm was high, as three-quarters of patients were assigned to rule-out or rule-in groups for NSTEMI, reported Dirk Westermann, MD, of University Heart Center Hamburg in Germany, and colleagues.

As shown in their study in the , basing the algorithm on hs-cTnI also worked, as patients with serial hs-cTnI measurements (n=3,500) gave the algorithm an NPV of 99.7% and a PPV of 62.3%. In this case, overall efficacy was lower, with 67% of patients assigned to NSTEMI rule-in and rule-out groups.

"No patient with NSTEMI was missed by both the hs-cTnT and the hs-cTnI algorithms," the researchers said. "The algorithm is very safe and effective in triaging patients with suspected NSTEMI."

The large multicenter study was aimed at addressing concerns over the suitability of ESC's new algorithm in routine clinical care, they explained. For the early triage of suspected NSTEMI patients presenting to the emergency department, the 0/1-h algorithm is recommended for use in combination with an electrocardiogram, chest pain characteristics, and all other clinical information.

"Our findings corroborate and extend previous work on the development and validation of safe and effective rule-out and rule-in strategies for NSTEMI and highlight that the hs-cTnT and hs-cTnI cutoff levels currently suggested by the ESC balance safety and efficacy well," Westermann's group wrote.

Questions About Methodology

However, in an accompanying editorial, two clinicians raised several concerns with the study's methodology.

For one, the validation studies of the hs-cTnI assay may possibly be wrong because it was extrapolated from the hs-cTnT assay, wrote Joseph Alpert, MD, of the University of Arizona College of Medicine in Tucson, and Allan Jaffe, MD, of the Mayo Clinic in Rochester, Minnesota.

There was also no information given on post-discharge care and testing of these patients, the editorial added. Importantly, the investigators excluded patients who were critically ill and the very elderly.

"In conclusion, the current study and other clinical investigations support the concept that many patients, particularly low-risk individuals who present at least 3 hours after the onset of symptoms, can have acute [myocardial infarction] excluded with high-sensitivity troponin testing, assuming FDA approval of the values used extensively in Europe and in this evaluation," Alpert and Jaffe wrote.

"Even then, however, caution is advised when dealing with patient subsets such as the elderly, the critically ill, individuals with endstage renal disease, those who present with atypical symptoms, and perhaps also those who present very early after the onset of symptoms. It is likely for these reasons and others that an employing this approach in an emergency medicine setting performed far less well than in the present study."

For the analyses, Westermann and colleagues pooled data from two ongoing studies in Europe (APACE and BACC) in which clinicians measured hs-cTnT and hs-cTnI at presentation and after 1 hour.

The final diagnosis was adjudicated by two independent cardiologists, who confirmed that 17% of the study population did have NSTEMI.