# Two-Hour Algorithm to Rule In or Rule Out Acute MI

Am Fam Physician. 2015 Aug 1;92(3):228a-230.

## Clinical Question

Can acute myocardial infarction (MI) be ruled in or ruled out within two hours of presentation using high-sensitivity troponin levels?

## Bottom Line

A simple rule (see synopsis) using high-sensitivity cardiac troponin levels measured on presentation and two hours later is an effective way to identify patients with or without MI. This rule was developed in one group of patients and validated in a second group. At a prevalence of 9%, this rule correctly ruled out MI 99.5% of the time. (Level of Evidence = 1a)

## Synopsis

Swiss investigators developed this rule by enrolling 1,148 unselected patients who presented to an emergency department with suspected MI. High-sensitivity cardiac troponin level was measured at presentation. The final diagnosis of MI, which occurred in 16% of these patients, was made by two cardiologists not involved in the study based on patient data collected over 60 days from the time of presentation. The rule was then validated on a separate set of 517 patients who presented to an emergency department at a hospital on a different continent (Australia), 9.1% of whom had MI. The rule identified 22% of the patients as definitely or possibly having MI and 78% of the patients were ruled out of having MI. Of the ruled-out patients, 100% were alive 30 days later. The resulting sensitivity for the rule-in algorithm was 96% and the specificity was 99% (positive predictive value = 85%; negative predictive value = 99.5%).

The rule (based on high-sensitivity troponin level obtained at presentation and at two hours):

• Rule out MI if the maximum troponin level is less than 14 ng per L (0.014 mcg per L) and the absolute change over two hours is less than 4 ng per L (0.004 mcg per L).

• Rule in MI if the maximum troponin level is greater than 52 ng per L (0.052 mcg per L) or the absolute change over two hours is greater than 9 ng per L (0.009 mcg per L).

• Further observe patients who are not in either of these categories.

Study design: Decision rule (validation)

Funding source: Industry plus government

Setting: Emergency department

Reference: Reichlin T, Cullen L, Parsonage WA, et al. Two-hour algorithm for triage toward rule-out and rule-in of acute myocardial infarction using high-sensitivity cardiac troponin T. Am J Med. 2015; 128( 4): 369– 379.

For definitions of levels of evidence used in POEMs, see http://www.essentialevidenceplus.com/product/ebm_loe.cfm?show=oxford.

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This series is coordinated by Sumi Sexton, MD, Associate Medical Editor.

A collection of POEMs published in AFP is available at https://www.aafp.org/afp/poems.

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