RT Journal Article SR Electronic T1 Site of psoriasis (scalp or intergluteal/perianal), ⩾3 affected sites, and nail dystrophy predicted psoriatic arthritis in incident psoriasis JF Evidence Based Medicine JO Evid Based Med FD BMJ Publishing Group Ltd SP 185 OP 185 DO 10.1136/ebm.14.6.185 VO 14 IS 6 YR 2009 UL http://ebm.bmj.com/content/14/6/185.abstract AB