HLA-B27

Reported as Negative or Positive (sometimes Absent or Present, or Not detected or Detected). About 8 in 100 people of white European background in the general population carry it, fewer in other groups, and the great majority never develop any related condition.

HLA-B27 is not an antibody or a chemical but a marker on the surface of the body's cells, part of the system the immune system uses to tell self from non-self. It is inherited and does not change through life. Carrying it is common and usually of no consequence, but it is found much more often in people with a group of conditions that cause inflammation of the spine and joints, so the test is used when looking at those.

Doctors request it when looking at long-standing back pain and stiffness that is worse in the morning and eases with movement, at some kinds of joint and eye inflammation (uveitis), and in the relatives of people with ankylosing spondylitis. It is done once, because the result never changes.

• Being positive is an inherited trait carried by about 8 in 100 people of white European background
• It is found in about 9 in 10 people with ankylosing spondylitis
• It is more common in people with reactive arthritis, psoriatic spinal arthritis and some kinds of uveitis

• Negative is the usual result; most people do not carry it
• The result is fixed from birth and does not change with illness, treatment or age
• Being negative does not exclude the related conditions, which also occur in people without it

• Most people who carry it never develop any related condition; a positive result on its own is simply an inherited trait
• Rarely, a different but closely related marker (such as B7) gives a false positive on some older methods

No fasting needed. It is a genetic marker, so a single test is all that is ever needed and it is never followed over time.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.