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[Usefulness of rapid quantitative cardiac troponin T and myoglobin assays for the diagnosis of acute myocardial infarction]. 2003
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. 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. The sensitivity of cTnT for identifying acute myocardial infarction was 76%, significantly higher than that of Mb (67%, p < 0.01) and CK-MB (54%, p < 0.05). The diagnostic sensitivities in patients admitted < or = 3 hr and 3-6 hr after onset were 52% and 65% for cTnT, 60% and 90% for Mb, and 36% and 50% for CK-MB, respectively. These sensitivities of Mb were significantly higher than those of CK-MB but not cTnT. However, the sensitivity of cTnT (100%) was significantly higher than that of Mb (58%, p < 0.01) and CK-MB (70%, p < 0.001) in patients admitted > 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. Bedside rapid quantitative assays of cTnT and Mb are useful as a point of care test for the diagnosis of acute myocardial infarction.
