What does capital-restricted meaning mean

Von, medical editor and biologist
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The abbreviation HLA-B27 stands for “Human Leukocyte Antigen B27”. It is a protein on the surface of almost all body cells - at least in people who have the blueprint for this protein in their genetic make-up. Certain inflammatory rheumatic diseases occur more frequently in these people. Read everything you need to know about HLA-B27 here!

What is HLA-B27?

HLA-B27 is one of the so-called human leukocyte antigens (HLA), also known as histocompatibility antigens (tissue compatibility antigens). These are proteins on the surface of almost all body cells that are very important for the immune system and for defense reactions.

There are different types of HLA proteins. Which of these occur in the body varies greatly from person to person.

The HLA variant HLA-B27 occurs rather rarely in the Western European population (only in around six to nine percent). It is of medical interest because it is often associated with certain inflammatory rheumatic diseases.

HLA-B27 can be detected frequently in:

  • Ankylosing spondylitis (Bechterew's disease)
  • Reactive arthritis (formerly Reiter's disease)
  • Psoriasis (arthritis)
  • Juvenile idiopathic arthritis
  • Crohn's disease
  • Certain eye inflammations, e.g. inflammation of the middle skin of the eye in the anterior area (anterior uveitis) or inflammation of the iris (iritis)
  • Rheumatoid arthritis

So people with HLA-B27 can be more prone to these conditions. We don't yet know why.

Strictly speaking, HLA-B27 is not fundamentally associated with an increased risk of disease. There are numerous subtypes of this antigen, some of which do NOT increase the risk of the diseases mentioned.

When is HLA-B27 determined?

The determination of HLA-B27 can be useful if the doctor suspects one of the diseases mentioned above in a patient - for example due to corresponding symptoms. The determination serves here as a confirmatory test. This can be helpful, for example, if ankylosing spondylitis is suspected - especially if the disease is still in its early stages or is very untypical and therefore makes a diagnosis difficult.

HLA-B27: Inheritance

The HLA-B27 test is not suitable as a screening test. That means: It does not make sense to have someone examined for HLA-B27 just like that (without a corresponding suspicion of illness) - for example a child if one of the parents is HLA-B27-positive and has ankylosing spondylitis. There are two reasons:

On the one hand, not all carriers of this antigen get ankylosing spondylitis (or one of the other diseases mentioned): According to studies, the probability that an HLA-B27-positive child of ankylosing spondylitis patient will also get the disease is less than ten percent.

On the other hand, according to the current state of medicine, an outbreak of disease cannot be prevented at all. Knowing whether a (still) healthy person has HLA-B27 or not has no practical use.

What is HLA-B27 determined from?

The doctor determines HLA-B27 in the blood. A simple blood test is sufficient for this. For the collection, the doctor uses a tube that contains a small amount of EDTA (ethylenediaminetetraacetic acid). Mixed with EDTA, the blood cannot clot - this is necessary for HLA-B27 determination.

If the doctor causes this due to typical complaints, both statutory and private health insurances usually pay the HLA-B27 test costs.

What does it mean to be HLA-B27 positive?

The detection of HLA-B27 does not mean much on its own. However, if the person concerned suffers from rheumatic complaints, for example, a positive HLA-B27 strongly suggests an actual illness.

HLA-B27 occurs particularly often in connection with ankylosing spondylitis: 87 to 95 percent of all ankylosing spondylitis patients have HLA-B27 in their blood. Symptoms of this chronic inflammatory joint disease, which mainly affects the spine, are mainly back, lower back and buttocks pain as well as stiff joints in the morning.

Some patients with reactive arthritis, psoriatic arthritis, or juvenile idiopathic arthritis are also HLA-B27 positive. The situation is different with rheumatoid arthritis: here only about one in ten patients has HLA-B27.

What does it mean to be HLA-B27 negative?

If no HLA-B27 can be detected, one of the diseases mentioned above may still be present. About 30 to 40 percent of all people with psoriatic arthritis are HLA-B27 negative. So if HLA-B27 is not detectable despite a suspected disease, the doctor will arrange further examinations to confirm the diagnosis.

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