ESC Rapid Rule-In, Rule-Out Algorithm for NSTEMI Safe, Accurate

Marlene Busko

August 29, 2017

BARCELONA, SPAIN — The European Society of Cardiology (ESC) 0/1-hour algorithm to "rule in" or "rule out" non-ST-segment-elevation MI (NSTEMI) in patients presenting to the emergency department with chest pain can quickly separate patients who need prompt treatment from those who can safely be discharged home, results of a large validation study suggest[1].

Dr Raphael Twerenbold

The findings "should give confidence in the high safety and applicability of this algorithm into daily clinical practice," Dr Raphael Twerenbold (Cardiovascular Research Institute, Basel, Switzerland) said during a press conference here at the European Society of Cardiology 2017 Congress.

Specifically, in more than 4000 patients with a suspected MI, the ESC 0/1-hour algorithm appropriately identified patients who likely had, did not have, or might have NSTEMI, based on levels of high-sensitivity troponin T or I (hs-cTnT or I) in blood samples drawn when the patient arrived in the emergency room and an hour later.

Importantly, the safety, accuracy, and efficacy of this algorithm were similar in patients who presented 3 or more hours after their chest pain started or those who presented earlier, with less obvious signs of MI.

"Most important, safety comes first," Twerenbold stressed to theheart.org | Medscape Cardiology. That is, it is crucial to spot patients who really do have an NSTEMI, he said, so that they are not discharged home.

"Efficacy comes second," he continued. That is, these high-sensitivity troponin levels at time 0 and 1 hour should be highly sensitive for triaging patients.

Applying the ESC 0/1 algorithm "is a game changer in the sense that the earlier you make the diagnosis, the sooner the patient is going to be directed to the right place" for treatment, which ups the odds of survival, ESC spokesperson Dr Sarah Catherine Clarke (Cambridge, United Kingdom), president of the British Cardiovascular Society, commented in an interview.

Triaging patients correctly "is very important in the crowded emergency room," she observed.

The ESC 2015 guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation[2] state that "used in conjunction with clinical and ECG findings, the 0/1-hour algorithm may allow the identification of candidates for early discharge and outpatient management."

"A lot of hospitals have changed their behavior and applied this 0/1-hour algorithm," ESC spokesperson Dr Josepa Mauri Ferré (Hospital Germans Trias I Pujol, Badalona, Spain), commented. This study "supports that it's a good thing to do."

Triage Safety Questioned in "Early Presenters"

The 2015 ESC guidelines state that the 0/1-hour algorithm can be used to quickly triage such patients.

"However, its safety has been questioned," Twerenbold said, "particularly in patients presenting very early after chest-pain onset, since small MIs might be missed in these high-risk patients."

In this analysis, the researchers aimed to validate the diagnostic performance of the ESC 0/1-hour algorithm using pooled data from two prospective studies: Advantageous Predictors of Acute Coronary Syndromes Evaluation (APACE) and Biomarkers in Acute Cardiovascular Care (BACC).

They retrospectively identified 4350 patients in these trials who presented with symptoms suggesting an acute MI, excluding patients with STEMI, in 14 centers in six European countries.

Of these, 743 patients (17%) were diagnosed with NSTEMI, based on central adjudication by two independent cardiologists. The patients had a mean age of 65, and 67% were male.

Blood levels of hs-cTnT (Elecys assay, Roche Diagnostics) and hs-cTnI (Architect i2000SR assay, Abbott Diagnostics) were determined from samples taken when the patients presented and then 1 hour later.

As specified in the algorithm, based on their hs-cTnT and hs-cTnI levels at time 0 and 1 hour, the patients were classified as "rule in," "rule out," or "observe" for NSTEMI.

Using hs-cTnT values at time 0 and 1 hour, the 0/1-hour algorithm safely ruled out patients who did not have NSTEMI. The negative predictive value was 99.8%, and the sensitivity was 99.3%.

Similarly, the algorithm accurately ruled in NSTEMI. The positive predictive value was 74.7%, and the specificity was 94.5%.

The algorithm was also very efficient in triaging patients to appropriate "rule in" or "rule out" NSTEMI categories. That is, three out of four patients (57% plus 18%) could be triaged into these two categories, leaving one-quarter who needed further observation.

Prediction of NSTEMI From hs-cTnT Levels at 0 and 1 Hour*

Rule out (n=2473) Observe (n=1088) Rule in (n=789)
Proportion 57 Proportion 25 Proportion 18
NPV 99.8 Prevalence of NSTEMI 14 PPV 74.5
Sensitivity 99.3     Specificity 94.5
NPV=negative predictive value
PPV=positive predictive value
*All values in %

Importantly, in the subset of 1289 patients who presented early, within 3 hours, "we can confirm very high safety (negative predictive value of 99.5%)," Twerenbold noted. The positive predictive value to rule in NSTEMI was 72.8%.

Again, three patients out of four could be triaged to "rule out" or "rule in" NSTEMI categories.

With the two hs-cTnI measurements, the negative predictive value to rule out NSTEMI was 99.6%, and the positive predictive value to rule in NSTEMI was 64.2%.

The hs-cTnI levels also had a high efficiency, allowing two out of three patients to be triaged to the "rule-out" or "rule-in" NSTEMI categories.

Prediction of NSTEMI, From hs-cTnI Levels at 0 and 1 Hour*

Rule out (n=1990) Observe (n=1395) Rule in (n=965)
Proportion 46 Proportion 32 Proportion 22
NPV 99.6 Prevalence of NSTEMI 8 PPV 64.2
Sensitivity 98.8     Specificity 90.4
NPV=negative predictive value
PPV=positive predictive value
*All values in %

The findings were similar in the subgroup of "early presenters."

"Many institutions in Germany and Switzerland have already switched to the 0/1-hour algorithm," Twerenbold noted.

The US Food and Drug Administration (FDA) has just cleared the first high-sensitivity troponin assay by Roche, and other assays will be approved soon, he added.

The researchers also investigated the diagnostic performance of the 0/1-hour algorithm in the US setting and that study will be published soon.

The APACE study was supported by research grants from the Swiss National Science Foundation, the Swiss Heart Foundation, the KTI, the European Union, the Stiftung für kardiovaskuläre Forschung Basel, Abbott, Beckman Coulter, Biomerieux, Brahms, Roche, Siemens, and Singulex. The BACC study was supported by the German Center of Cardiovascular Research and an unrestricted grant from Abbott Diagnostics. The investigation's high-sensitivity cardiac troponin T and I assays were donated by Roche and Abbott, which had no role in the design of the study, the analysis of the data, the preparation of the manuscript, or the decision to submit the manuscript for publication. Twerenbold reports receiving research support from the Swiss National Science Foundation and speaker honoraria/consulting honoraria from Roche Diagnostics, Abbott Diagnostics, Siemens, and Brahms.

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