Diagnostic accuracy, angiographic correlates and long-term risk stratification with the troponin T ultra sensitive Rapid Assay in chest pain patients at low risk for acute myocardial infarction.

Abstract

This prospective study of acute chest pain patients clinically at low risk for a myocardial infarction was designed to: determine the diagnostic accuracy of a cardiac troponin T (cTnT) ultra sensitive Rapid Assay (RAII) compared with the quantitative cTnT assay; evaluate the association of a positive RAII with the presence and severity of coronary artery disease (CAD); and determine the ability of the RAII result to predict adverse events during long-term follow-up. A total of 199 patients referred for chest pain, without ST segment elevation on presenting ECG, underwent RAII, quantitative cTnT, CK and CK-MB tests drawn simultaneously > or = 10 h after symptom onset. An abnormal value for cTnT was defined as >0.1 ng.mL(-1). The presence and extent of CAD was recorded in patients undergoing angiography. Adverse events, including cardiac death, non-fatal infarction, and readmission for unstable angina or heart failure, were assessed long-term. An abnormal RAII was found in 41 (20-6%) patients. The RAII sensitivity for detecting abnormal quantitative cTnT levels was 100%, specificity 96.3% (158/164) and overall concordance 97.5%. Although the presenting ECG was normal or non-specific in 95%, ST depression or T wave inversion occurred in 17% of RAII-positive versus 2%, RAII-negative patients (P=0.004). Of RAII-positive patients who underwent angiography (79%), 87% had CAD and 60% had multivessel disease. Kaplan Meier event-free survival curves showed early separation and continued to modestly diverge for patients with positive and negative RAII (69% versus 90% one-year event-free survival, P=0.002). In a chest pain population anticipated to have a low prevalence of acute coronary syndromes and a good prognosis, the RAII is a quick and reliable test. It provides an important initial opportunity to identify patients with a high prevalence of CAD and increased incidence of future cardiac events.