1 Department of Internal and Integrative Medicine, Kliniken Essen-Mitte, Faculty of Medicine, University of Duisburg-Essen, 45276 Essen, Germany.
2 Department of Internal Medicine 1, Klinikum Saarbrücken, 66119 Saarbrücken, Germany ; Department of Psychosomatic Medicine and Psychotherapy, Technische Universität München, 81865 München, Germany.
3 Service de Médecine Interne et Thérapeutique, Centre de la Douleur, Hôtel Dieu, Université Paris Descartes, INSERM U 987, Paris, France.
4 Department of Rheumatology, Hospital Universitari Vall d'Hebron, Barcelona, Spain.
5 Rheumatology Unit, L Sacco University Hospital, Milan, Italy.