[1] Univ Oxford, Nuffield Dept Orthopaed Rhuematol & Musculoskelet, Oxford, England
[2] Hosp Santa Maria, Rheumatol Res Unit IMM, Rheumatol, Lisbon, Portugal
[3] Southend Univ Hosp, Rheumatol, Southend On Sea, Essex, England
[4] Berlin Buch, Med Ctr Rheumatol, Rheumatol, Berlin, Germany
[5] Hosp Southern Norway HF, Rheumatol, Kristiansand, Norway
[6] London Sch Hyg & Trop Med, Dept Hlth Serv Res & Policy, London WC1, England