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Measurement of muscle proteins may help ER doctors triage acute coronary syndrome patients who have normal ECGs

Patients with acute coronary syndromes (ACS) are at risk of heart attack, other major cardiac complications, and death. ACS patients who arrive at the emergency department (ED) with chest pain often have normal electrocardiograms (ECGs) with no evidence of ST-segment elevation or new, pathologic Q-waves, which complicates triage decisions. ED physicians end up admitting some of these patients to the hospital for unnecessary intensive monitoring or inappropriately sending home some who are actually at high risk of heart attack or death. Measurement of troponin, a complex of muscle proteins that inhibit contraction, may help identify which ACS patients with normal ECGs should be hospitalized and which can be sent home, according to a recent study supported by the Agency for Healthcare Research and Quality (contract 290-97-0013).

Researchers at the University of California, San Francisco-Stanford Evidence-based Practice Center conducted an in-depth review of the evidence, including clinical trials and cohort studies of consecutive patients with suspected ACS without ST-elevation published between 1966 and 1999. Overall, 7 clinical trials and 19 cohort studies reported data for 5,360 patients with a troponin T test and 6,603 with a troponin I test. In ACS patients with normal ECGs (non-ST elevation) who had an abnormal troponin test, the short-term odds of death were increased three- to eight-fold.

Cohort studies (which usually have more heterogeneous patients than highly selected patients of clinical trials) demonstrated an even greater difference in mortality between patients with a positive versus negative troponin I (8.4 vs. 0.7 percent) than clinical trials (4.8 vs. 2.1 percent). The prognostic value of a positive troponin T test also was slightly greater for cohort studies (11.6 vs. 1.7 percent) than for clinical trials (3.8 vs. 1.3 percent).

See "The prognostic value of troponin in patients with non-ST elevation acute coronary syndromes: A meta-analysis," by Paul A. Heidenreich, M.D., M.S., F.A.C.C., Thomas Alloggiamento, M.D., Kathryn Melsop, M.S., and others in the August 2001 Journal of the American College of Cardiology 38(2), pp. 478-485.

Editor's Note: This study is drawn from Evidence Report/Technology Assessment No. 31, Prediction of Risk for Patients with Unstable Angina. Print copies of the full report (AHRQ Publication No. 01-E001) are available from the AHRQ Publications Clearinghouse and a report summary (AHRQ Publication No. 00-E030) is available from the AHRQ Publications Clearinghouse.

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