[1] Univ Penn, Perelman Sch Med, Philadelphia, PA 19104 USA
[2] Univ Penn, Perelman Sch Med, Ctr Clin Epidemiol & Biostat, Philadelphia, PA 19104 USA
[3] Univ Penn, Dept Biostat Epidemiol & Informat, Philadelphia, PA 19104 USA
[4] Univ Penn, Dept Dermatol, Div Dermatol Surg & Cutaneous Oncol, Perelman Ctr Adv Med, Philadelphia, PA 19104 USA