[1] McGill Univ, Ctr Hlth, Div Rheumatol, Montreal, PQ, Canada
[2] McGill Univ, Ctr Hlth, Div Clin Epidemiol, Montreal, PQ, Canada
[3] Univ Calgary, Div Rheumatol, Calgary, AB, Canada
[4] Northwestern Univ, FSM, Chicago, IL 60611 USA
[5] Oklahoma Med Res Fdn, Arthrit & Clin Immunol Res Program, 825 NE 13th St, Oklahoma City, OK 73104 USA
[6] Univ British Columbia, Sch Populat & Publ Hlth, Vancouver, BC, Canada
[7] Beckman Res Inst, Div Canc Etiol, Dept Populat Sci, Duarte, CA USA
[8] Kings Coll London, Dept Med & Mol Genet, London, England