Preanalytics: The patient should lie during blood drawing. 1 day before the patient should abstain from coffee, tea, bananas, oranges and other citrus fruits no drugs like paracetamol, aspirin, aminophyllin, chloralhydrate, clonidine, dexamethason or duretics. Blood should be centrifugated immediately, plasma can be stored up to 2 hours at room temperature, for longer storage plasma samples should be kept frozen at -20 °C.