1. Faculty of Medicine, University of Niš, 18000 Niš, Serbia
2. COVID Hospital Kruševac, University Clinical Centre of Niš, 37000 Kruševac, Serbia
3. Clinic of Gastroenterohepatology, University Clinical Centre of Niš, 18000 Niš, Serbia
4. General Hospital Leskovac, Department of General Surgery with Traumatology, 16000 Leskovac, Serbia
5. Faculty of Medicine, University of Priština, 38220 Kosovska Mitrovica, Serbia
6. Pediatrics Clinic, Clinical Centre Priština, 38205 Gracanica, Serbia
7. Clinic for Cardiovascular and Transplant Surgery, Faculty of Medicine, University Clinical Centre of Niš, 18000 Niš, Serbia
8. Institute of Physiology and Biochemistry “Ivan Djaja”, Faculty of Biology, University of Belgrade, 11000 Belgrade, Serbia
9. Institute for Biochemistry, Faculty of Medicine, University of Niš, 18000 Niš, Serbia