A blood test for HLA B-27, also known as human leukocyte antigen B-27, is used to detect the presence of a protein (HLA B-27) that is found on the surface of white blood cells. HLA B-27 may be a sign of an autoimmune condition when the body's own cells are attacked by the guarding cells (WBC). If you have chronic joint pain, stiffness, or inflammation in your lower back, you should get this test. It may also be suggested in cases of eye irritation, particularly in men. Autoimmune conditions like rheumatoid arthritis and reactive arthritis are more likely to manifest in people with HLA B-27. Inflammatory bowel disease and other chronic diseases are allegedly connected to B-27.