Human leukocyte antigen B27 (HLA-B27) is a protein located on the surface of your white blood cells. An HLA-B27 test is a blood test that identifies HLA-B27 proteins. These antigens help your immune system identify the differences between healthy body tissue and foreign substances that may cause infection.
The presence of HLA-B27 is associated with certain autoimmune and immune-mediated diseases, including:
ankylosing spondylitis, reactive arthritis, juvenile rheumatoid arthritis, anterior uveitis
A negative test indicates the absence of HLA-B27 in your blood. If the test is positive, this means that HLA-B27 is present in your blood. Although a positive result may be cause for concern, the presence of the antigen doesn’t always mean that an autoimmune disorder will develop.
