[1] Univ Toronto, Dept Med, Div Rheumatol, Toronto, ON, Canada
[2] Univ Hlth Network, Toronto Western Hosp, Psoriat Arthrit Program, Ctr Prognosis Studies Rheumat Dis, Toronto, ON M5T 2S8, Canada
[3] NYU, Sch Med, Div Rheumatol, Arthrit Clin, New York, NY USA
[4] NYU, Sch Med, Div Rheumatol, Psoriat Arthrit Ctr, New York, NY USA