1. Department Clinical Biochemistry, North Denmark Regional Hospital, DK-9800 Hjørring, Denmark
2. National Addiction Centre, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, SE5 8BB London, UK
3. Centre for Clinical Research, North Denmark Regional Hospital, DK-9800 Hjørring, Denmark
4. Department of Clinical Medicine, Aalborg University, DK-9100 Aalborg, Denmark