HLA-B27 Blood Tests

The HLA-B27 test is a blood test used to identify the presence of a specific protein on the surface of white blood cells, which is part of the human leukocyte antigen (HLA) system. HLA-B27 is one of the many variants of the HLA-B gene. This test is particularly significant because the presence of HLA-B27 is associated with certain autoimmune disorders and rheumatic conditions.

Purpose of the HLA-B27 Test:

1. Diagnosis of Autoimmune Conditions:
   • Ankylosing Spondylitis: HLA-B27 is strongly associated with ankylosing spondylitis, a type of arthritis that primarily affects the spine, causing inflammation, pain, and potentially leading to fusion of the vertebrae. Approximately 80-90% of individuals with ankylosing spondylitis are HLA-B27 positive.
   • Other Conditions: HLA-B27 is also associated with other forms of spondyloarthritis such as reactive arthritis (formerly known as Reiter's syndrome), certain forms of juvenile arthritis, and psoriatic arthritis.
2. Assessing Risk:
   • While the presence of HLA-B27 does not confirm that a person will develop these diseases, it significantly increases the likelihood compared to the general population. The test can be used to assess the risk in patients presenting with symptoms of these disorders or in a diagnostic context when these conditions are suspected.