Test Details: GAD-65 antibody test is useful to diagnose Insulin dependent Diabetes mellitus (IDDM) and development of related endocrine disorders like Thyroiditis. It is also used to diagnose Stiff Man syndrome & automimmune encephalitis. Antibodies to glutamic acid decarboxylase (anti-GAD) are reliable serological markers of Insulin-dependent diabetes mellitus. Anti-GAD antibodies in high titre are associated with the stiff-person syndrome (60% sensitivity), a rare neurological disease characterised by muscle rigidity and spasms. Core manifestations of GAD65 neurological autoimmunity are SPSD, cerebellar ataxia, epilepsy and LE.