Time Window Of Ruling Out Myocardial Infarction With Troponin T And Creatine Kinase MB Mass

Objective To research the sensitivity and specificity of troponin I (TnI) for the diagnosis of acute myocardial infarction (AMI). To investigate the time window for ruling out AMI with TnI and creatine kinase isoenzyme MB mass (CK-MBm). Methods According to the inclusion and exclusion criteria to choose the final study population among 161 unselected and consecutive patients with chest pain or equivalent symptoms in the Emergency Department. The blood samples for the measurement of TnI and CK-MBm concentrations were drawn at 0, 3, 6, 9, 12 and 24h after admission in the Emergency Department. Results The final study population comprised 95 patients. Among them, 35 were diagnosed as AMI with the gold standard, and 32 were diagnosed as AMI with TnI. The sensitivity of TnI is 91% with 95% CI from 82%to 100% and the specificity is 93% with 95% CI from 87% to 99%. Among 35 cases AMI, AMI diagnosis was confirmed with elevated TnI(>1.5ng/ml) in 86% within 12-24 h from the onset of symptoms, and in 89% within 12h from admission. In 31 of these CK-MBm became elevated (>5.0ng/ml), in 90%within 9-12 h from the onset of symptoms and in 94% within 6h from admission. Conclusion For patients with chest pain or equivalent symptoms, there are both high sensitivity and specificity of TnI for diagnosis of AMI. Using TnI or CK-MBm, AMI can be ruled out within 12 h from admission in the majority of patients.