HLA-B27
A genetic tissue type carried by some people. It is not a disease in itself, but it is strongly associated with a family of inflammatory conditions of the spine, joints and eyes — such as ankylosing spondylitis, reactive arthritis and recurrent uveitis — so testing for it supports the diagnosis when these are suspected.
What it measures
HLA-B27 is one of many human leukocyte antigens — proteins on the surface of cells that help the immune system tell 'self' from 'foreign'. Everyone inherits a set of these tissue types; HLA-B27 is simply one particular variant, present in roughly 6–8% of people of European descent. The test reports whether you carry it (positive) or not (negative), and the result never changes because it is genetic. HLA-B27 itself is not a disease and most people who carry it stay perfectly well. Its value is as a supporting clue: it is strongly associated with the 'spondyloarthritis' family of inflammatory conditions, above all ankylosing spondylitis (inflammation of the spine and pelvis), and also reactive arthritis, the arthritis linked to inflammatory bowel disease and psoriasis, and recurrent acute anterior uveitis (a painful red eye from inflammation). Because it is common in healthy people, a positive result does not diagnose anything on its own — it raises or lowers the probability of these conditions in someone who already has suggestive symptoms, and is interpreted alongside the clinical picture, inflammatory markers and imaging.
What a high value can mean
- A positive result — you carry HLA-B27; most carriers remain healthy, but it raises the likelihood of spondyloarthritis in someone with suggestive symptoms.
- Supports ankylosing spondylitis — in a person with chronic inflammatory back pain.
- Supports reactive arthritis — arthritis following a gut or genital infection.
- Associated with recurrent acute anterior uveitis — a painful, red, inflamed eye.
- Linked to arthritis with inflammatory bowel disease or psoriasis.
What a low value can mean
- A negative result — you do not carry HLA-B27; this makes the associated conditions less likely but does not exclude them, as they can still occur without it.
When to discuss with a doctor
HLA-B27 is a targeted test, ordered when a doctor suspects a spondyloarthritis-type condition — for example chronic inflammatory back pain that is worse at rest and better with movement, arthritis after an infection, or recurrent painful red eyes. It is never a screening test for healthy people, because carrying it is common and usually harmless, and a positive result in someone without symptoms means little. When it is used, it is one piece of the picture alongside symptoms, inflammatory markers (ESR, CRP) and imaging of the spine and joints. Mediora.AI shows an HLA-B27 result in the context of the inflammatory markers and the conditions it points to, so it is read as a clue rather than a verdict; the diagnosis belongs with your doctor, usually a rheumatologist.