Original Contributions
Prediction of short- and long-term outcomes by troponin t levels in low-risk patients evaluated for acute coronary syndromes,☆☆

Presented at the Society for Academic Emergency Medicine annual meeting, Chicago, IL, May 1998, and the 8th Annual Midwest Regional Emergency Medicine Research Symposium, Columbus, OH, April 1998.
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Abstract

Study objective: Recent reports suggest a short series of cardiac troponin (cTnT) testing effectively identifies patients at risk for cardiac events. However, there are few studies validating this strategy. The purpose of this study was to determine the ability of cTnT levels to predict short- and long-term outcomes in low-risk patients with suspected acute coronary syndromes. Methods: This prospective longitudinal study was conducted in a 20-bed emergency department observation unit. Patients at low risk for acute coronary ischemia, with a normal creatine kinase–isoenzyme subunit MB (CKMB) index, were admitted to an observation unit for chest pain evaluation. Serum cTnT levels were measured at baseline and at 4, 8, and 16 hours after admission. The main outcome measures were adverse cardiac events (death, acute myocardial infarction, unstable angina, revascularization) during the index visit and within 6 months after discharge. Using manufacturer’s recommendations, the cTnT level was considered abnormal if it exceeded 0.2 μg/L. Results: Two hundred sixty-six patients were evaluated. Twenty-one (7.9%) had an adverse event during their index hospitalization. Troponin testing identified only 2 (9.5%) of these patients. Twenty (7.5%) had a cardiac event within 6 months; none were identified by cTnT testing. The sensitivity and specificity were 9.5% and 99.2%, respectively, at the index visit, and 0% and 98.4% at 6 months. The positive and negative predictive values were 50% and 93%, respectively, at the index visit; and 0% and 92% at 6 months. Conclusion: Determination of troponin T levels has a low sensitivity and high specificity for predicting outcomes in low-risk patients evaluated for suspected acute coronary syndromes. This study does not support a strategy of relying solely on troponin testing for disposition decisions. [Peacock WF IV, Emerman CL, McErlean ES, Deluca SA, van Lente F, Rao JS, Nissen SE: Prediction of short- and long-term outcomes by troponin T levels in low-risk patients evaluated for acute coronary syndromes. Ann Emerg Med. March 2000;35:213-220.]

Section snippets

INTRODUCTION

Chest pain is a common but difficult problem to assess in the emergency department. Observation and serial testing are used to overcome the limitations of the initial history, physical examination, ECG, and enzyme assay results.1 Between 2% and 5% of patients with chest discomfort are inappropriately discharged from the ED,2, 3, 4, 5 but only about one third of patients admitted with suspected acute coronary syndromes ultimately have a diagnosis of myocardial infarction.6 An accurate marker of

MATERIALS AND METHODS

We conducted a prospective longitudinal study in a convenience sample of low-risk patients admitted to the observation unit in the ED of a large, urban, academic tertiary care center. This was part of a larger program examining the value of troponin T testing in all patients with suspected acute coronary syndromes. The annual ED census is approximately 40,000 patients, of whom 9% have an acute chest pain syndrome. Nearly 4% of ED patients with an acute chest pain syndrome are immediately

RESULTS

Two hundred sixty-six patients were studied with a mean age of 59.8±14.0 years; 139 (52.3%) were women. One hundred twenty-eight (48.1%) of the patients were white and 125 (47%) were black. The mean time to presentation was 5 hours after symptom onset. Average time of follow-up was 6.3 (±0.9) months. At the 6-month evaluation, all patients had complete follow-up. Most patients (94%) had at least one historical cardiac risk factor, with an average of 3.2±1.9 risk factors per patient.

Because an

DISCUSSION

In patients with AMI, many studies have found cTnT testing to be a useful diagnostic test.7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 However, none have evaluated the prospectively defined low-risk acute coronary syndrome ED patient. Hamm et al8 suggested that negative results on serial troponin testing are associated with such low risk as to allow rapid and safe discharge of ED patients. They recommended that patients with suspected acute coronary syndromes, but with 2 normal troponin

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    Supported by a grant from Boehringer-Mannheim.

    ☆☆

    Address for reprints: William Franklin Peacock IV, MD, Emergency Department, E19, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195; 216-445-4546, fax 216-445-4552;E-mail [email protected] .

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