USE OF TROPONIN-T AND CREATINE KINASE-MB SUBUNIT LEVELS FOR RISK STRATIFICATION OF EMERGENCY DEPARTMENT PATIENTS WITH POSSIBLE MYOCARDIAL-ISCHEMIA

Study Objectives: To evaluate and compare the utility of measurement o f troponin T and the creatine kinase MB subunit (OK-MB) for risk strat ification of ED patients with possible myocardial ischemia. Methods: P rospective observational study of ED patients with symptoms of possibl e myocardial ischemia with early, single sample serologic testing for cardiac troponin T and CK-MB using an identity-unlinked process. Chart review (ED, inpatient, outpatient), and telephone and mail surveys id entified adverse events (AEs) during the 14 days following enrollment. AEs recorded included death, respiratory or cardiac arrest, myocardia l infarction (MI), atrial and ventricular arrhythmias, pulmonary edema , conduction disturbances, and recurrent angina. Measures of the predi ctive ability for AEs were calculated for troponin T, CK-MB, and a com bined troponin T/CK-MB index (defined as positive if either troponin T or CK-MB levels exceeded threshold values). Results: Among 292 study patients, 45 (15.4%) experienced al least one AE, including seven deat hs and 12 Mis. The troponin T result was positive in 34 patients, and the CK-MB result was positive in 15 patients; 6 patients had positive results for both markers and 43 patients had a positive combined tropo nin T/CK-MB index. Odds ratios (ORs) for occurrence of AEs among all p atients were 4.4(1.8 to 10.2), 10.0 (3.0 to 36.0), and 4.5 (2.0 to 9.8 ) for troponin T, CK-MB, and the troponin T/CK-MB index, respectively. Both markers were individually predictive of AEs (troponin T=4.3; CK- MB=7.5) among all those with chest pain. Only the CK-MB level was sign ificantly predictive of AEs among those presenting with symptoms other than chest pain (OR=24.3 [1.1, 1448]), whereas only the troponin T le vel was significantly predictive among patients representing a disposi tion dilemma for the emergency physician (OR=5.7 [1.4, 20.7]). When co mpared, the ORs for troponin T and CK-MB were not significantly differ ent for any patient subgroup. The troponin T/CK-MB index did not have a higher prognostic value than either troponin T or CK-MB alone in any subgroup studied. Conclusion: A positive test result for either tropo nin T or CK-MB in the ED successfully identified patients at significa ntly higher risk of adverse events during the 2 weeks following their ED visit. The two markers may complement each other in that each appea rs to have prognostic ability among a unique patient subgroup. ED mark er measurement can provide useful prognostic information for patients with a broad spectrum of presentations consistent with possible myocar dial ischemia.