1. Faculty of Medicine, Medical University of Sofia, Boulevard “Akademik Ivan Evstratiev Geshov” 15, 1431 Sofia, Bulgaria
2. Division of Clinical Immunology and Rheumatology, Department of Internal Medicine, University Hospital Centre Zagreb, School of Medicine, University of Zagreb, Kispaticeva 12, 10000 Zagreb, Croatia
3. Second Specialised Hospital for Obstetrics and Gynaecology “Sheynovo”, ul. Sheinovo 19, 1504 Sofia, Bulgaria
4. Medical Faculty, Sofia University, St. Kliment Ohridski, 1 Kozyak Str., 1407 Sofia, Bulgaria
5. Department of Rheumatology, Clinic of Rheumatology, University Hospital St Ivan Rilski, Urvich Str. 13, 1612 Sofia, Bulgaria