[1] Diakonhjemmet Hosp, Dept Rheumatol, N-0319 Oslo, Norway
[2] Univ Oslo, Fac Med, Oslo, Norway
[3] Leiden Univ, Med Ctr, Dept Rheumatol, Leiden, Netherlands
[4] Univ Hosp Maastricht, Dept Rheumatol, Maastricht, Netherlands
[5] Univ Hosp, Rikshosp, Inst Immunol, Oslo, Norway
[6] Univ Hosp Ulleval, Dept Immunol & Transfus Med, Oslo, Norway