1. Division of Rheumatology, Center for Clinical Epidemiology and Biostatistics, Center for Pharmacoepidemiology Research and Training
2. Department of Dermatology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
3. Division of Rheumatology, Landspitali University Hospital, University of Iceland, Reykjavik, Iceland
4. Division of Rheumatology, Philadelphia Veterans Administration Medical Center, Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
5. Division of Rheumatology, Allergy, and Immunology, Massachusetts General Hospital, Harvard Medical School, Boston, MA
6. Department of Dermatology, Center for Clinical Epidemiology and Biostatistics, Center for Pharmacoepidemiology Research and Training, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA