Time-dependent diagnostic performance of a rapid troponin T version 2 bedside test in patients with acute coronary syndromes

Abstract

In a prospective trial, the diagnostic performance of the second version of the troponin T rapid assay (Trop T; cutoff 0.2 microg/L) was compared with the quantitative cardiac-specific troponin T assay (cTnT ELISA; cutoff 0.1 microg/L) and other established cardiac markers such as CK, CK-MB activity, CK-MB mass and myoglobin. Additionally, a 30-day follow-up was performed to determine the suitability of the Trop T assay and the reference markers for short-term risk stratification. Two-hundred-and-eighty-six consecutive patients with chest pain and suspected acute myocardial infarction (AMI) were enrolled in two CCU departments. Serial blood specimens were taken at admission and at 3, 6, 12, 24, 48, 72 and 96 h after admission. According to the biochemical criterion CK-MB mass, the patients were classified as having AMI in 154 patients (54%), unstable angina (UAP) in 72 patients (27%) and no evidence for acute cardiac ischemia in 55 patients (19%). Analytical method comparison of Trop T with cTnT ELISA (cutoff 0.1 microg/L) showed a good agreement, Trop T yielded only 4% false-negative and 3% false-positive results. The diagnostic performance of Trop T for the detection of AMI was only slightly inferior compared to cTnT ELISA. Beyond 12 h after admission, Trop T and cTnT ELISA maintained a sensitivity close to 100%, whereas the sensitivity of the other cardiac markers decreased sharply. The diagnostic sensitivity of Trop T for the detection of minor myocardial damage in UAP patients was the same as for cTnT ELISA. Death within 30 days' follow-up occurred only in AMI patients with a positive Trop T test result within the first 6 h after admission. The admission Trop T and cTnT ELISA were the only significant biochemical predictors of major cardiac events. In conclusion, these data show that Trop T has similar diagnostic sensitivity as cTnT ELISA and is a useful tool to confirm acute or subacute myocardial infarction. Trop T is an excellent marker in detecting minor myocardial damage in UAP patients and is suitable for short-term risk stratification.