[1] Diakonhjemmet Hosp, Oslo, Norway
[2] Rigshosp, Ctr Rheumatol & Spine Dis, Copenhagen Ctr Arthrit Res, Glostrup, Denmark
[3] Hosp Southern Norway Trust, Kristiansand, Norway
[4] Diakonhjemmet Hosp, Dept Rheumatol, Oslo, Norway
[5] Univ Oslo, Fac Med, Oslo, Norway