1. Department of Public Health and Clinical Medicine/Rheumatology, University of Umeå, 901 87 Umeå, Sweden
2. Department of Surgical and Perioperative Sciences, University of Umeå, 901 87 Umeå, Sweden
3. Department of Rheumatology, Östersund Hospital, 831 27 Östersund, Sweden
4. Department of Rheumatology, Sunderby Hospital, 971 89 Luleå, Sweden