Single troponin test at ED admission may be enough to rule out acute MI
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Researchers at the Kaiser Permanente Health System observed that a single troponin test at ED admission for patients with suspected ACS may be enough to rule out acute MI and reduce hospital stay.
“Our study suggests that patients are routinely discharged from the ED after a single negative troponin test result, and when compared with serial troponin testing, a single troponin test appears safe based on current physician decision-making, with no difference in rates of 30-day cardiac mortality and acute MI, which are low in both groups,” Adam L. Sharp, MD, MSc, emergency physician at the Kaiser Permanente Los Angeles Medical Center and research scientist in the department of research and evaluation, told Healio. “Our interpretation of these results supports physician-patient shared decisions to consider a single undetectable troponin result sufficient among patients with symptoms less than 3 hours with a low-risk HEART score.”
For this retrospective cohort study published in JAMA Network Open, researchers included 27,918 ED encounters with suspected ACS, a HEART score (history, ECG, age, risk factors and troponin) and an initial troponin I measurement of less than 0.02 ng/mL (mean age, 59 years; 58% women). The primary outcome was acute MI or cardiac mortality. The secondary outcomes included CABG, PCI, invasive coronary angiography and unstable angina within 30 days of discharge.
Single vs. multiple troponin measurements
Of patients with an initial troponin measurement less than 0.02 ng/mL, 51.8% were discharged after a single measurement and 48.2% underwent serial troponin tests.
After adjustment for cardiac risk factors and comorbidities, researchers reported no statistically significant difference within 30 days in rates of acute MI or cardiac mortality between the single and multiple troponin test groups (0.4% vs. 0.4%; adjusted OR = 1.41; 95% CI, 0.96-2.07).
“Many experts agree that there is broad overuse of troponin tests for clinical presentations even when the suspicion for acute MI is low,” Maereg Wassie, MD, fellow in cardiology at Kaiser Permanente Southern California, and colleagues wrote. “When the troponin test was first introduced for clinical use, it was thought to be specific for acute MI because the population in which it was studied had a significantly higher prevalence of coronary artery disease. However, its current use in the general population and with high-sensitivity troponin has made it less specific for acute MI when results are positive.”
In other findings, patients discharged after a single troponin test experienced lower rates of CABG (aOR = 0.24; 95% CI, 0.11-0.48) and invasive coronary angiography (aOR = 0.46; 95% CI, 0.38-0.56).
Researchers observed no significant difference in the rates of PCI (OR = 0.73; 95% CI, 0.44-1.18) and unstable angina (OR = 1.05; 95% CI, 0.76-1.44) between the single and multiple troponin test groups.
‘Major implications regarding current practice’
“In recent years, there has been substantial interest in the question of whether discharge after a single troponin measurement is safe. The HEART and T-MACS (troponin-only Manchester ACS) scores were designed to facilitate safe discharge after a single blood test,” Barbra Eva Backus, MD, PhD, emergency physician at Erasmus Medical Center in the Netherlands, and colleagues wrote in a related editorial. “Furthermore, with high-sensitivity cardiac troponin (hs-cTn) assays, there is now an abundance of data to suggest that according to the hs-cTn assay used, acute myocardial infarction can be safely ruled out in patients who have a troponin concentration less than the limit of detection or less than the limit of quantification.
“It is a surprising finding in the study by Wassie et al that half of ED clinicians used a single troponin measurement before discharging patients with chest pain. This has not been previously described in a study of this size, in which 30-day outcome data were available,” Backus and colleagues wrote. “This has major implications regarding current practice in the United States; it can no longer be said that current ED practice involves obtaining serial troponin measurements on all patients with chest pain; of note, of the 13,459 patients with a repeated troponin tests in this study, only 66 (0.5%) had a subsequently positive troponin test.”
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Adam L. Sharp, MD, MSc, can be reached at adam.l.sharp@kp.org.
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