[1] Univ Penn, Sch Med, Dept Biostat & Epidemiol, Ctr Clin Epidemiol & Biostat, Philadelphia, PA 19104 USA
[2] Univ Penn, Sch Med, Dept Dermatol, Philadelphia, PA 19104 USA
[3] Univ Penn, Dept Med, Div Pulm, Philadelphia, PA 19104 USA
[4] Univ Dundee, Div Mol Med, Coll Life Sci & Med, Dundee, Scotland
[5] Univ Dundee, Coll Dent & Nursing, Dundee, Scotland