Abstract

Objective: To assess the diagnostic efficiency of the third generation cardiac troponin T assay in routine clinical practice.

Design: Prospective observational study of unselected consecutive admissions.

Setting: Multicentre study in 43 teaching and non-teaching hospitals in 13 countries.

Subjects: 1105 hospital admissions, median age 67 years (range 15–96 years, 63.7% male) with suspected acute coronary syndromes (72.3% of cases) or other non-specific symptoms where cardiac disease required exclusion (27.7%).

Interventions: Over the study period, myoglobin, creatine kinase MB isoenzyme (CK-MB), and cardiac troponin T where measured in parallel with conventional diagnostic tests. Final diagnostic classification involved standard ECG changes and CK-MB mass exceeding 5.0 μg/l.

Main outcome measures: Diagnostic efficiency was assessed by receiver operator characteristic curve analysis including and excluding patients with unstable angina.

Results: Measurement of cardiac troponin T was diagnostically equivalent to CK-MB and both were better than myoglobin, with areas under the curve at 12 hours of 0.94, 0.99, and 0.80, respectively. Diagnostic criteria using CK-MB were inadequate and showed bias when patients with unstable angina were included. Elevations of cardiac troponin T did not occur when cardiac disease could be categorically excluded but were found in clinical conditions other than suspected acute coronary syndromes.

Conclusions: CK-MB is unsuitable as a diagnostic gold standard even at the proposed lower threshold. A lower cut off for cardiac troponin T of 0.05 μg/l should be used for diagnosis of acute myocardial infarction. Diagnosis of acute myocardial infarction cannot be made solely on the basis of a cardiac troponin T result.