<qa>  What is the cause of pain determined with the help of the ischemic marker?Patients in a Chest Pain Unit CPU are examined to clarify if the cause of pain is cardiac or not. To identify patients with ST-elevation and other electrocardiogram ECG modifications a normal 12-lead ECG is used. The diagnosis non-st-elevation myocardial infarction is determined with the help of the ischemic marker Troponin. However, Troponin levels are elevated earliest 3 to 4 hours after the ischemic event, so that a negative Troponin result at the time of hospital admission is insufficient. Thus the guidelines of the German Society of Cardiology demand a second measurement after 6 to 12 hours. In rare cases false positive Troponin levels have been reported e.g. in patients with renal insufficiency. 