Usefulness of rapid quantitative cardiac troponin T and myoglobin assays for the diagnosis of acute myocardial infarction

BACKGROUND AND OBJECTIVES: The rapid cardiac troponin T (cTnT) test is widely used to detect myocardial necrosis in the emergency setting. This assay system is rapid and myocardial-specific, but the plasma cTnT concentration is difficult to determine quantitatively. A recently developed bedside cTnT and myoglobin (Mb) analyzer (CARDIAC system) was evaluated. METHODS: The new CARDIAC system was used to measure plasma cTnT and Mb levels, and serum levels of creatine kinase MB isoenzyme (CK-MB), cTnT and Mb were measured by conventional assays in 160 consecutive emergency patients with suspected acute myocardial infarction. RESULTS: The sensitivity of cTnT for identifying acute myocardial infarction was 76%, significantly higher than that of Mb (67%, p 6 hr after onset. The specificities of cTnT, Mb and CK-MB were 96%, 76% (p < 0.001 vs cTnT and CK-MB) and 95%, respectively. Therefore, cTnT (86%) had significantly (p < 0.001) higher diagnostic accuracy compared with Mb (71%) and CK-MB (75%). Combination diagnosis using cTnT and Mb showed the highest sensitivity (86%) compared with cTnT (p < 0.05) and Mb (p < 0.001). The correlation coefficients between the levels measured by CARDIAC system and those by ordinary assays were 0.98 in cTnT and 0.97 in Mb. CONCLUSIONS: Bedside rapid quantitative assays of cTnT and Mb are useful as a point of care test for the diagnosis of acute myocardial infarction.