Conventional Troponin Testing in the Evaluation of Chest Pain

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Is it safe to do one and done?

History

Chest pain is one of the most common reasons for Emergency Department (ED) visits. While most of these presentations are at a low risk for cardiac events, it is generally required to perform a full work-up to rule out an Acute Coronary Syndrome (ACS), including an Acute Myocardial Infarction (AMI), before being discharged responsibly.


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The biggest challenge for physicians is to not only to identify patients who are likely to have ACS, but also to identify low risk patients that can be safely discharged without prolonged stays for further investigation. The current standard of practice, including risk assessment protocols, recommends using serial troponin testing and detection of absolute changes in troponin levels to rule out AMI in the ED.

Recent studies using high sensitivity troponin (hsTnT) have shown that if the initial troponin is very low, one troponin may be sufficient to safely discharge patients from the ED, especially when combined with the HEART score. In practice however, in countries where hsTnT is not generally available, some clinicians have adopted this strategy using conventional troponin despite a lack of supporting research.

Study Findings


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Wassie M, et al. published an article on JAMA Network Open [1] of their study into whether discharging patients from the ED after a single contemporary troponin test with negative results has similar outcomes to patients undergoing multiple troponin tests. They conducted a retrospective analysis of data prospectively collected from 15 community EDs using the same conventional troponin-I (cTnI) assay between Jan. 1, 2015 to Dec. 31, 2017 in Southern California.

Among the study cohort were adult patients presenting to the ED with chest pain suspected of having ACS with a HEART-score and an initial conventional troponin-I level below the limit of quantification (<0.02 for this assay). Patients with a Do-not-resuscitate (DNR) or hospice status were excluded.

The HEART score was calculated using clinical and demographic data, categorizing patient scores as low (0 to 3), moderate (4 to 6), or high risk (7 to 10) to aid clinical decision making. Education was provided to physicians to encourage repeat troponin testing at least three hours after symptom onset or after the peak of symptom severity.

Physicians were encouraged to use timing of symptoms, initial troponin value and initial HEART score to determine the need for repeat troponin testing and further clinical management. The majority of repeat troponin tests were placed three to six hours after the initial troponin was drawn. Unfortunately, data for the timing of the onset of chest pain was not available for this study.


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The primary outcome of this study was AMI or cardiac mortality 30-days after ED discharge, secondary outcomes were unstable angina, invasive coronary angiography, percutaneous transluminal coronary angioplasty (PTCA), and coronary artery bypass graft (CABG).

Results

A total of 27,918 patients were included in the final analysis.  A single troponin was ordered in 51.8% of patients. Patients with a single troponin test were younger and less likely to have comorbid conditions including hypertension, diabetes, lipid disorders, renal failure and/or congestive heart failure.

Generally, these patients had a lower HEART-score as well. Serial troponin orders were made in 48.2%, with 10.2% having more than two serial measurements. Only 66 patients with a serial troponin test (0.5%) had a subsequent positive troponin.

Wassie et al. found no statistically significant difference between risk of AMI or cardiac mortality at 30 days when comparing patients who underwent serial troponin testing to patients discharged after a single negative troponin test (0.4% vs. 0.4%). Patients discharged after a single negative troponin test result had lower adjusted rates for the secondary outcomes, including unstable angina, invasive coronary angiography, PTCA, and CABG.

This large population-based study reflects the practice pattern in multiple community-based EDs across Southern California. It investigated a diverse and realistic population and has follow-up information for all the patients. It was performed with a conventional troponin assay which is currently widely used in the US.

Given the observational study design, causality cannot be assumed, and residual confounding may be present despite adjustments of multiple variables. The diagnosis of AMI was made by reviewing the Emergency Medical Record and was not adjudicated.

Specific data on the HEART score versus outcome per participant was also not reported. The dataset used in this analysis lacks several granular details that are regularly available in trials and registries, particularly the timing of symptom onset which may be a key variable in determining which patients benefit most from serial testing.

Currently, the AHA and ESC both recommend serial cardiac troponins to identify and exclude AMI. This is due to the potential slow rise and the late peak of troponin.  Most patients presenting to the ED with chest pain are low risk for ACS and/or have had prolonged symptoms and may not benefit from repeat troponin testing despite these guideline recommendations.

Conclusion

Wassie et al. demonstrate that in clinical practice the single conventional troponin strategy is safe when performed along with a clinician’s clinical assessment and risk stratification by the HEART score. The study also demonstrates that physicians are able to appropriately identify patients at higher risk based on other clinical factors beyond a second troponin test.

The study of Wassie et al. shows that over 50% of physicians already use a low-risk HEART score and a single contemporary troponin test before discharging patients with chest pain home. And to emphasize, only 66 patients (0.5%) with serial troponin testing had a subsequent positive troponin test, which again is still below the generally accepted 1% threshold of missed diagnoses.

Cardiac mortality was slightly higher in the single troponin group compared to serial troponin group (0.02% vs. 0.07%); however, this was not statistically significant.

The ability to effectively and promptly rule out AMI using a single contemporary troponin allows rapid and accurate discharge of low-risk patients. This significantly reduces the need to keep patients in the ED for serial troponin testing and thus reducing healthcare costs, and ED overcrowding by reducing ED length of stay.

Discharging patients presenting to the ED with chest pain after a single negative conventional troponin and proper risk stratification with the HEART score can be considered as safe as serial troponin testing while being less time consuming, less costly and therefore more patient-oriented.

Reference:

  1. Wassie et al. Single versus serial measurements of cardiac troponin in the evaluation of emergency department patients with suspected acute myocardial infarction. JAMA Network Open 2021.

ABOUT THE AUTHORS

Barbra Backus, MD is an emergency physician at the Erasmus University Medical Center in the Netherlands. She developed and validated the HEART score for chest pain patients at the emergency department and finished her thesis on HEART in 2012. She continued her research specialty on low-risk chest pain. Dr. Backus has co-authored several books and blogs on cardiology & emergency medicine and is part of the editorial board of EJEM.

Benjamin M. Gerretsen, MD (@bmgerretsen) is currently a first-year emergency medicine resident at Reinier de Graaf Gasthuis, the Netherlands. 

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