Connective tissue diseases (CTDs) are systemic rheumatologic diseases that can affect all compartments of the respiratory tract, including airways, alveoli, interstitium, vessels, and pleura. Usually, they are characterized by the presence of over-activity of the immune system by unknown causes, which results in the production of autoantibodies which attack against organ unspecific antigens of the nucleus and cytoplasm. The common CTDs include rheumatoid arthritis (RA), systemic sclerosis (SSc), dermatomyositis/polymyositis (DM/PM), mixed connective tissue disease (MCTD), systemic lupus erythematosus (SLE), Sjögren's syndrome (SS), relapsing polychondritis, and ankylosing spondylitis. Autoantibodies which target against antigens located in the nucleus is so-called anti-nuclear antibodies (ANAs). ANAs are important serological markers for diagnosis of CTDs. Generally, ANAs include extractable nuclear antigen (ENA) antibodies and un-extractable nuclear antigen antibodies. HOB offers a comprehensive portfolio to screen, differentiate and monitor autoantibodies for the effective diagnosis of many connective tissue diseases.