In the diagnostic setting of ACS, expression and functionnaly activity of A2AR could be a sensitive detection method for ischemia. It would be a powerful tool for risk stratification of patients presenting with chest pain but unremarkable ECG and blood tests. the investigateors therefore designed a blind multicentrique prospective study to evaluate expression and functionnaly activity of A2AR in the management of undifferentiated chest pain The objective of the study was to evaluate diagnostic accuracy between this novel biomarkers A2AR and invasive and non -invasive evaluation of patients with suspected coronary artery disease (CAD).