1. Department of Epidemiology and Biostatistics, Faculty of Medicine, University of Iceland, Reykjavik, Iceland
2. Department of Rheumatology, University Hospital, Reykjavik, Iceland
3. Centre for Rheumatology Research, University Hospital, Reykjavik, Iceland
4. Department of Pathology, Akureyri Regional Hospital, Akureyri, Iceland
5. Clinical Epidemiology Research and Training Unit, Boston University School of Medicine, Boston, MA, USA
6. Faculty of Medicine, University of Iceland, Reykjavik, Iceland
7. Icelandic Heart Association, Kopavogur, Iceland
8. Division of Rheumatology, University of Pennsylvania, Philadelphia, PA, USA
9. Department of Biostatistics, Epidemiology, and Informatics, University of Pennsylvania, Philadelphia, PA, USA