 When a patient is presenting with acute chest pain at the ER of the University Hospital of Zurich, the study physician in charge, who is acting simultaneously as one of four attending clinical physicians, is performing the physical examination according to routine clinical practice. The physical examination includes the testing of chest wall tenderness: Palpation of chest wall tenderness in lying 30 elevation of chest position. Flat index with standardized pressure where spontaneous maximum pain is reported reproducible vs. not reproducible pain vs. no pain. Negative control right side of chest mid-clavicle intercostal 67, reproducible vs. not reproducible pain vs. no pain. The same physician, who is blinded for the final diagnosis at the time of the physical examination, is also recording the patient history including the study interview using the standardized study questionnaire. 