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Rapid Assessment of Possible ACS With hs-TnT: RAPID-TnT Study
Study Questions:
How does the safety of a 0/1-hour high-sensitivity troponin T (hs-cTnT) protocol compare to a 0/3-hour protocol in patients presenting to the emergency department (ED) with suspected acute coronary syndrome (ACS)?
Methods:
The RAPID-TnT trial involving four metropolitan EDs in Adelaide, Australia, randomized 3,378 adult patients with suspected ACS but without an electrocardiogram definitive for coronary ischemia to either a 0/1-hour hs-cTnT arm (n = 1,646) or a standard 0/3-hour hs-cTnT arm (n = 1,642) following the statewide chest pain protocol. If baseline hs-cTnT was <5 ng/L over 3 hours since onset of symptoms, or ≤12 ng/L with <3 ng/L change over 1 hour, participants were discharged with primary care follow-up. Admission was recommended for a baseline troponin ≥52 ng/L or a 1-hour change ≥5 ng/L was documented. Observation and repeat testing were recommended for intermediary values. The primary outcome was 30-day all-cause death and myocardial infarction (MI).
Results:
The median age of participants was 59 (interquartile range, 49-70) years, while 47% were women, and 28% had a prior history of coronary artery disease. There were no significant differences in clinical characteristics between study arms. The incidence of 30-day death or MI was the same in both groups (1.0%, p for noninferiority = 0.006). Among participants randomized to the 0/1-hour protocol, 136/1,646 (8%), 308/1,646 (19%), and 1,187/1,646 (72%) were considered “rule-in MI,” “observe,” and “rule-out MI,” respectively. Amongst those “ruled-out” in the 0/1 hour, five patients (0.4%) experienced the primary endpoint. Negative predictive value for the 0/1-hour arm was 99.6%. Re-hospitalization within 30 days was also similar between groups (13.5%). The 0/1-hour arm was associated with a higher rate of direct discharge from the ED (45% vs. 33% for the standard arm), and less frequent referral for further functional cardiovascular testing. Length of stay was shorter among those in the 0/1-hour arm (median of 4.6 vs. 5.6 hours in the standard arm).
Conclusions:
A 0/1-hour hs-cTnT rapid triage strategy is as safe as a 0/3-hour protocol in ruling out MI in patients presenting to the ED with suspected ACS.
Perspective:
This study is the latest in a string of trials confirming the safety of a 0/1-hour hs-Tn protocol in the management of ED patients with suspected ACS. In this study, patients were randomized on presentation at EDs, rather than randomizing the different EDs to specific strategies. Thus, the authors noted a longer ED length of stay and rate of hospitalization compared to previous studies, which was attributed to the cautious approach of ED physicians in the adoption of a new protocol. Despite several differences compared to other studies, the 0/1-hour hs-TnT protocol appears to be safe, and reduces length of stay. As similar protocols are implemented and refined, the benefits of rapid triage will become more apparent.
Keywords: Acute Coronary Syndrome, Arrhythmias, Cardiac, Chest Pain, Electrocardiography, Emergency Service, Hospital, Myocardial Infarction, Myocardial Ischemia, Secondary Prevention, Stroke, Troponin, Troponin T
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