What is HLA-B27 blood test?

HLA-B27 test is a blood test to look for the HLA-B27 gene. This gene predisposes to a number of autoimmune diseases including Ankylosing spondylitis, Reactive arthritis & uveitis.

When is HLA-B27 test ordered?

Your Rheumatologist will order HLA-B27 test if he suspects Ankylosing spondylitis, reactive arthritis. The suspicion is raised by inflammatory backache or pain/ swelling in knee/ ankle/ feet joints.

What does a positive HLA-B27 test mean?

A positive test means that the person carries the HLA-b27 gene. One inherits the gene from his/ her parents. This is not a diagnostic test. It does not mean that the person has Ankylosing spondylitis. A negative test does not rule out Ankylosing spondylitis.

How does HLA-b27 lead to Ankylosing spondylitis?

HLA-b27 gene plays an important role in helping the body distinguish between self & foreign proteins. You may know more about its role in causation of Ankylosing spondylitis on my blog.