[1] Karolinska Inst, Dept Med, Rheumatol Unit, Stockholm, Sweden
[2] Univ Amsterdam, Med Ctr, Dept Rheumatol & Clin Immunol, Rheumatol & Immunol Ctr ARC, Amsterdam, Netherlands
[3] Karolinska Inst, Karolinska Univ Hosp, Dept Med, Rheumatol Unit, Stockholm, Sweden
[4] Rigshosp, DANBIO, Glostrup, Denmark
[5] Rigshosp, Ctr Rheumatol & Spine Dis, COPECARE, Glostrup, Denmark
[6] Diakonhjemmet Hosp, Oslo, Norway
[7] Helsinki Univ Hosp, Div Internal Med & Rheumatol, Helsinki, Finland
[8] Univ Amsterdam, Med Ctr, Amsterdam Rheumatol & Immunol Ctr, Amsterdam, Netherlands
[9] Univ Iceland, Landspitali Univ Hosp, Reykjavik, Iceland
[10] Univ Gothenburg, Sahlgrenska Univ Hosp, Sahlgrenska Acad, Rheumatol Clin, Gothenburg, Sweden
[11] Rigshosp, Ctr Rheumatol & Spine Dis, Copenhagen Ctr Arthrit Res, Glostrup, Denmark
[12] Univ Copenhagen, Dept Clin Med, Glostrup, Denmark
[13] Univ Oslo, Diakonhjemmet Hosp, Oslo, Norway
[14] Univ Southern Denmark, Danish Hosp Rheumat Dis, Reykjavik, Iceland
[15] Univ Eastern Finland, Jyvaskyla Cent Hosp, Jyvaskyla, Finland
[16] Univ Amsterdam, Med Ctr, Dept Epidemiol & Biostat, Amsterdam, Netherlands
[17] Vrije Univ Amsterdam, Med Ctr, Dept Rheumatol, Amsterdam, Netherlands