Prehospital identification of acute coronary ischemia using a troponin T rapid assay

To evaluate the performance of a rapid assay for cardiac troponin T (cTn-T) in patients with chest pain in the prehospital setting.

A prospective, observational clinical trial in a rural county served by a single emergency medical services system and two emergency departments. Patients fulfilling prehospital criteria to identify acute coronary ischemia (ACI) had a blood sample applied to the cTn-T rapid-assay device. Quantitative analysis of cTn-T was also performed on each sample at a later time. Medical records were reviewed to determine ultimate diagnoses. Non-admitted patients were followed by telephone at one week. Main outcome measures included the sensitivity, specificity, positive predictive value, and negative predictive value of the rapid cTn-T assay for detecting ACI defined as acute myocardial infarction (AMI) or unstable angina (UA) within one week of presentation.

Of 87 patients enrolled, 29 were identified with ACI. This included 15 patients diagnosed as having AMI and 14 patients diagnosed as having UA. The cTn-T rapid-assay device was positive for five of 87 patients (5.7%); three were associated with AMI and two with UA. Measurement of a single cTn-T to detect ACI had a sensitivity of 17.2% (0.058, 0.358), specificity of 100% (0.950, 1), positive predictive value of 100% (0.549, 1), and negative predictive value of 70.7% (0.609, 0.806).

The cTn-T rapid-assay device may be useful in the prehospital setting to identify a small number of patients with ACI. The authors caution, however, that a negative test in the prehospital setting cannot be used to rule out significant disease.