Single testing with high-sensitivity troponin effective, safe for early rule-out of MI
A single testing of cardiac troponin I using a high-sensitivity assay can effectively rule out myocardial infarction (MI) without compromising safety, according to the HiSTORIC* study presented at the ESC 2019 Congress.
Implementing the high-sensitivity cardiac troponin I (hs-cTnI) assay significantly reduced the length of stay** by 3.3 hours compared with the standard care pathway using the 99th percentile at presentation as a cutoff for rule-out.
“Reducing length of stay by 3 hours could save more than US$3.6 billion annually on bed occupancy alone,” said lead investigator Professor Nicholas Mills from the University of Edinburgh in Edinburgh, UK.
“If we can make an evaluation that is safe with a single test on presentation to hospital, avoiding hospital admission and all the downstream investigations that certainly in many healthcare systems are standard practice, then the cost savings of this single test when used effectively could be absolutely enormous,” he stressed.
Participants in the stepped-wedge cluster randomized trial were 31,492 patients (mean age 59 years, 45 percent women) who presented with cardiac troponin I concentrations below the 99th percentile at the ED. In this trial, randomization was done at the hospital level instead of the patient level. The study involved three phases: a validation phase (6–9 months) during which all hospitals used a standard-care pathway, follow by a 6-month randomization phase whereby hospitals transitioned step-wise into the High-STEACS early rule-out pathway, and an implementation phase (6–9 months) when all centres were using the early rule-out pathway.
The primary efficacy endpoint of length of hospital stay was significantly shorter by 3.3 hours when using the early rule-out pathway vs the standard pathway (mean, 6.8 vs 10.1 hours; p<0.0001). [ESC 2019, abstract 2309]
Also, more patients got sent home from the ED during implementation of the early rule-out pathway compared with standard care (74 percent vs 53 percent; p<0.0001).
"So overall, three quarters of all patients with suspected acute coronary syndrome were managed in our outpatient setting," said Mills. "There are lots of practical reasons why I think this should be the way we triage patients with acute chest pain.”
Although noninferiority was not demonstrated for the primary safety endpoint of MI or cardiac death at 30 days (0.3 percent vs 0.4 percent), there was no notable increase in adverse cardiac events at 1 year (adjusted odds ratio, 1.02, 95 percent CI, 0.74–1.40).
An 'easy to use' pathway
Under the early rule-out pathway, a hs-cTnI concentration of <5 ng/L at presentation was considered as low risk and discharged home. The hs-cTnI threshold was based on a recent finding showing a negative predictive value of ≥99.5 percent for MI or cardiac death at 30 days. On the other hand, those presenting with levels between 5 ng/L and the 99th percentile underwent retesting after 3 hours and discharged if hs-cTnI was <3 ng/L or admitted if ≥3 ng/L. [Circulation 2019;doi: 10.1161/CIRCULATIONAHA.119.042866]
Describing the pathway as “simple, pragmatic, and easy to use”, Mills said the pathway allows clinicians to identify low-risk patients who can be safely discharged from the ED and focus on high-risk patients without compromising safety.
He also pointed out that the findings present a shift away from the concept that every positive troponin is a heart attack.
While complimenting the study as an “urgently needed and well-conducted trial … using validated cTnI discriminators”, invited discussant Dr Hugo Katus from Heidelberg University Hospital, Germany, cautioned that not all TnI assay is validated.
He also questioned whether HiSTORIC really investigated an early-rule-out protocol, noting that the time from presentation to blood sampling was longer (66 minutes) than the 60 minutes recommended by the ESC guidelines.