Evaluation of a rapid qualitative test for cardiac troponin T in clinical diagnosis of patients with acute coronary syndrome

Abstract

To evaluate the practical performance and the diagnostic power of a rapid, qualitative assay for the detection of cardiac Troponin T (indicated cut-off level: 0.3 ng/ml) in EMS patients presenting with acute myocardial ischemia. 145 consecutive patients with non-traumatic chest pain treated by the Mobile Intensive Care Unit team. During phase 1 (73 patients), blood drawn at the emergency site was used to perform a Troponin T rapid assay under defined conditions at the hospital. During phase 2 (72 patients), the rapid assay was already performed at the emergency site. In phase 1 all tests were performed correctly, whereas 5.6% of the test results had to be declared invalid in phase 2. 17 (11.7%) of the 145 patients showed a positive test result. Analytic sensitivity was 100%, specificity 96.3%. 37 of the 145 patients (median duration of symptoms: 150 minutes) showed a myocardial infarction (MI). Related to the diagnosis of MI diagnostic sensitivity, specificity, positive and negative predictive values were 35.1, 96.3, 76.5, and 81.3%. Mortality in patients with a positive rapid assay was 35.3%, compared to 6.3% in patients with a negative test result (p < 0.001). The rapid assay allows the detection of Troponin T in concentrations above the cut-off level. Meticulous observance of the manufacturer's rules is imperative. A single preclinical rapid assay does not allow to exclude a MI. However, the test enables EMS personnel to identify patients who are at increased risk of dying from an acute coronary syndrome in the immediate future.