1 Department of Hygiene, Epidemiology and Medical Statistics, Medical School, National and Kapodistrian University of Athens, Athens, Greece.
2 National Public Health Organization, Athens, Greece.
3 Department of Gastroenterology, Medical School, National and Kapodistrian University of Athens, General Hospital of Athens "Laiko", Athens, Greece.
4 Joint Rheumatology Program, First Department of Propaedeutic Internal Medicine, Medical School, National and Kapodistrian University of Athens, Athens, Greece.
5 Department of Internal Medicine, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece.
6 Second Department of Paediatrics, "P. & A. Kyriakou" Children's Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece.