HBV/HDV

Prospective, non-pharmacological, single-center, non-profit observational study. The study design allows longitudinal evaluation of the immune response during the natural history of the infection and/or treatment, correlating the data with the outcome of the disease and antiviral therapies, which will be collected as study variables from the source documents. The study population will be patients suffering from chronic HBV infection with or without HBV-HDV co-infection followed at the Division of Gastroenterology and Hepatology of Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico. The present study is part of an international cooperation project between the Division of Gastroenterology and Hepatology, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico (Milan, Italy) and the Duke-NUS Medical School, Singapore, financed by a grant (project MAECI-2023-23683653) and divided into two specific Work Packages: * WP 1 Milan team (WP1.1 - Clinical and virological phenotyping of CHB and CHD patients; WP1.2 - Clinical evaluation of rapid HBV T cell test in CHB and CHD populations) * WP 2 Singapore team (WP2.1 - Applicability of the rapid T cell assay approach; WP 2.2 - Optimization of the rapid T cell assay protocol) The primary objective of the study is to define the prevalence of specific T cell responses in patients with chronic HBV and HBV-HDV infection, through the application of a specific rapid T cell assay.