1. Section for Social Medicine, Institute of General Practice and Community Health, Faculty of Medicine, University of Oslo, Norway, , The National Resource Centre in Rheumatology, Diakonhjemmet Hospital, Norway
2. HØKH, Research Centre, Akershus University Hospital, Norway, Faculty Division Akershus University Hospital, University of Oslo, Norway
3. HØKH, Research Centre, Akershus University Hospital, Norway
4. Section for Social Medicine, Institute of General Practice and Community Health, Faculty of Medicine, University of Oslo, Norway