1. a Department of Internal Medicine I , Klinikum Saarbrücken , Saarbrücken , Germany
2. b Department of Psychosomatic Medicine and Psychotherapy , Technische Universität München , München , Germany
3. c Department of Pain Management , Berufsgenossenschaftliches Universitätsklinikum Bergmannsheil GmbH Bochum, Ruhr University Bochum , Bochum , Germany
4. d National Data Bank for Rheumatic Diseases , Wichita , Kansas
5. e University of Kansas School of Medicine , Wichita , Kansas , USA