The HLA B27 Test is a blood test used to detect the presence of the HLA-B27 protein on the surface of white blood cells. This specific protein is associated with a higher risk of developing certain autoimmune diseases, such as ankylosing spondylitis, reactive arthritis, and other related inflammatory conditions. While the presence of HLA-B27 does not confirm a diagnosis, it helps doctors evaluate the likelihood of these disorders when symptoms like chronic joint pain or inflammation are present. The test is simple and quick, typically requiring just a blood sample, and plays an important role in guiding further diagnostic and treatment decisions.