1. Department of Medical Sciences, Section of Clinical Chemistry, Uppsala University, 751 85 Uppsala, Sweden
2. Pain and Rehabilitation Center, and Department of Health, Medicine and Caring Sciences, Linköping University, 581 83 Linköping, Sweden
3. Department of Surgical Sciences, Section of Anaesthesiology and Intensive Care Medicine, Uppsala University, 751 85 Uppsala, Sweden
4. NOVA Medical School, New University of Lisbon, 1099-085 Lisbon, Portugal