The leukocyte antigen HLA-B27 is a marker of susceptibility to some rheumatic diseases such as ankylosing spondylitis (AS), reactive arthritis, arthritis/spondylitis associated with psoriasis, arthritis/spondylitis associated with inflammatory bowel disease and undifferentiated spondyloarthritis.
It can also be positive in certain patients with uveitis or psoriasis. Traditionally, testing for HLA-B27 was a great help to diagnose AS since it may be positive in up to 90% of AS patients. However, the diagnostic value of this test is very limited since a positive test for HLA-B27 antigen may be found in healthy population and a negative test for HLA-B27 does not rule out AS or related disorders.
Among rheumatologist, it is widely accepted that, in the absence of any suggestive symptoms or positive radiological findings, HLA-B27 HAS NOT ANY DIAGNOSTIC VALUE. The diagnosis of AS and related disorders is based upon a combination of a patient's symptoms, physical examination, and imaging tests.
In case you have a positive test for HLA-B27 antigen is highly recommended to find an expert that interprets its clinical significance depending on your symptoms and radiological findings.