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Prognostic Value of Undetectable hs Troponin T in Suspected Acute Coronary Syndrome

Patient flow. In the Biomarkers in Cardiology (BIC)-8 main trial, 902 patients were enrolled. Of these, 20 patients did not have high-sensitivity troponin T (hsTnT) or copeptin values available at admission. Thus, the study population of this BIC-8 substudy consists of 882 patients with complete biomarker results at admission. Patients were divided by their biomarker test. Relative and absolute frequencies are shown in the respective boxes.

Patient flow. In the Biomarkers in Cardiology (BIC)-8 main trial, 902 patients were enrolled. Of these, 20 patients did not have high-sensitivity troponin T (hsTnT) or copeptin values available at admission. Thus, the study population of this BIC-8 substudy consists of 882 patients with complete biomarker results at admission. Patients were divided by their biomarker test. Relative and absolute frequencies are shown in the respective boxes.

 

Background

The search for improved strategies for safe and early discharge of patients with suspected acute coronary syndrome in emergency departments is ongoing. This Biomarkers in Cardiology (BIC)-8 biomarker substudy evaluated the usefulness of high-sensitivity troponin T (hsTnT) below or above the limit of detection (LoD) in low-to-intermediate-risk patients with suspected acute coronary syndrome in the emergency department.

Methods

Patients were categorized into hsTnT ≥ the 99th percentile, between the 99th percentile and LoD, or undetectable hsTnT (<LoD). HsTnT and copeptin were measured at admission, using a copeptin cut-off of 10 pmol/L. The primary endpoint was death and myocardial infarction within 90 days after admission.

Results

Of 882 patients with all biomarker results, 577 (65.4%) had detectable hsTnT levels (≥LoD). Among the 305 patients (34.6%) with undetectable hsTnT, no myocardial infarctions or deaths occurred within 90 days. In patients with detectable hsTnT at admission (≥LoD but ≤99th percentile), the combined endpoint occurred in 1.5% (6/410) of the copeptin-negative patients and in 6.3% (6/96) of copeptin-positive patients within 90 days (hazard ratio 4.39; 95% confidence interval, 1.42-13.61; P = .01). In patients with an initially elevated hsTnT (≥14 ng/L), 9.7% (3/31) of the copeptin-negative patients and 15.4% (4/26) of the copeptin-positive patients experienced the combined endpoint (hazard ratio 1.61; 95% confidence interval, 0.36-7.17; P = .536).

Conclusions

In low-to-intermediate-risk patients with suspected acute coronary syndrome, undetectable hsTnT values at admission allow a safe discharge without occurrence of death or myocardial infarction within 90 days.

One of the challenging tasks of emergency departments and chest pain units is ruling out acute myocardial infarction. Chest pain is the leading symptom in about 10% of patients admitted to emergency departments, of whom only 10% are diagnosed to have an acute myocardial infarction. Guidelines demand serial measurements of cardiac biomarkers (preferentially cardiac troponins) for safe rule-out of acute myocardial infarction. Using a high-sensitivity troponin (hsTn) assay at the recommended cut-off value at the 99th percentile of a healthy reference population, patients require observation for at least 3 hours and retesting of hsTn to achieve an appropriate sensitivity for safe rule-out of acute myocardial infarction.

Several authors have investigated using lower cut-offs for earlier rule-out of acute myocardial infarction in patients with suspected acute coronary syndrome. The limit of blank (LoB) might be hampered by inappropriate assay precision and by potential bias from a lot-to-lot variation. A recent Swedish registry on 14,636 patients demonstrated an excellent negative predictive value (NPV) for acute myocardial infarction at 30 days of 99.8% (95% confidence interval [CI], 99.7-99.9) of a high-sensitivity troponin T (hsTnT) value below the limit of detection (LoD, 5 ng/L) combined with an electrocardiogram (ECG) without signs of ischemia for the rule-out of acute myocardial infarction. However, 21% of patients with hsTnT below the LoD were still admitted to the hospital, limiting conclusions on the safety of their discharge. The Biomarkers in Cardiology-8 (BIC-8) main study pursued a different concept, using simultaneous copeptin and troponin measurement for diagnosis and management of suspected acute coronary syndrome in the emergency department. The major finding of that study was that patients with negative troponin and negative copeptin values at admission could be discharged as safely as the standard group managed according to current guidelines. This BIC-8 biomarker substudy constitutes a postrandomization cohort evaluating a lower hsTnT decision cut-off at the LoD.

 

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-Mehrshad Vafaie, MD1, Anna Slagman, VD, MSc1, Martin Möckel, MD, PhD, Christian Hamm, MD, PhD, Kurt Huber, MD, PhD, Christian Müller, MD, Jörn O. Vollert, MD, MBA, Stefan Blankenberg, MD, PhD, Hugo A. Katus, MD, PhD, Christoph Liebetrau, MD, Evangelos Giannitsis, MD, PhD1, Julia Searle, MD, MPH

This article originally appeared in the March 2016 issue of The American Journal of Medicine.

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