1. Division of Epidemiology; Department of Health Research and Policy; Stanford School of Medicine; Stanford CA
2. Division of Immunology and Rheumatology; Department of Medicine; Stanford School of Medicine; Stanford CA
3. Clinical Epidemiology Unit; Department of Medicine; Karolinska University Hospital; Stockholm Sweden
4. Rheumatology Unit; Department of Medicine; Karolinska University Hospital; Stockholm Sweden
5. Department of Clinical Sciences; Karolinska Institute; Danderyd Hospital; Stockholm Sweden
6. Department of Pediatrics; University of California; San Diego, La Jolla CA
7. Division of Rheumatology; Hospital for Special Surgery; Weill Cornell Medical College; New York NY