1. Department of Clinical Immunology, University Hospital “Lozenetz”, Sofia University “St. Kliment Ohridski”, Sofia 1407, Bulgaria
2. Clinic of Endocrinology, University Hospital “Alexandrovska, ” Department of Internal Medicine, Medical Faculty, Medical University of Sofia, Sofia 1431, Bulgaria
3. Clinic of Internal Medicine, Naval Hospital-Varna, Military Medical Academy, Varna 9010, Bulgaria
4. Clinic of Rheumatology, University Hospital “St. Marina, ” First Department of Internal Medicine, Medical Faculty, Medical University-Varna, Varna 9010, Bulgaria