Superiority of combined CK-MB and troponin I measurements for the early risk stratification of unselected patients presenting with acute chest pain

Background: Recent studies have suggested that positive troponin I tests ar e associated with an increased risk of cardiac death during short-term foll ow-up. However, it is unknown if troponin I tests alone or in addition to C K-MB measurements are superior to predict unfavorable outcome during long-t erm follow-up. Patients and Methods: In a prospective, double-blind study w e assessed the prevalence and prognostic value of combined troponin I and C K-MB tests in an unselected cohort of patients (n = 292) admitted to the em ergency department for acute chest discomfort. Patients were grouped accord ing to the diagnosis on discharge in those with acute myocardial infarction (1), unstable angina (2), and noncardiac chest pain (3). Six months after enrollment, death rates were obtained, and follow-up interviews were perfor med with respect to survival, recurrence of chest pain, and myocardial infa rction. Results: In patients with evidence of coronary heart disease, the m ortality rate for abnormal troponin I and normal CK-MB levels was 5.0%, Bas eline troponin I and elevated CK-MB levels were associated with a mortality rate of 4.0%. However, the mortality rate was significantly higher (11.1%) in patients presenting with elevated troponin I and CK-MB values. In patie nts without myocardial infarction on admission, 10.5% with positive troponi n I tests died compared to 1.6% with negative tests. The mortality rate in patients without myocardial infarction was 2.7% for patients with elevated CK-MB but normal troponin I values. In patients with both markers elevated a significantly higher mortality rate (16.7%) was found, representing a 6-f old increase in the death event rate. With the additional knowledge of trop onin I values, it could be demonstrated that certain cases were misclassifi ed as having noncardiac chest pain. At least some of the latter patients wi th above-normal values of troponin I were retrospectively to be reclassifie d as unstable angina. Acute non-Q-wave myocardial infarctions were occasion ally misdiagnosed as either angina pectoris or nonischemic chest pain. Conc lusion: Our data suggest the superiority of combined. CK-MB and troponin I measurements in clinical practice for the early risk stratification of pati ents-presenting with acute chest pain. In nonmyocardial infarctions, both C K-MB and troponin I convey independent prognostic information with regard t o fatal outcome. Troponin I tests in addition to CK-MB measurements contrib ute to a lower rate of misdiagnoses.