When you have symptoms of chronic inflammation, pain, and stiffness in certain areas of your body, such as your back, neck, and chest, or the interior portion of your eyes uveitis, especially if you are male and the symptoms began between late teens and your early 30s
A blood sample taken from a vein in your arm
HLA-B27 is a particular antigen found in certain people and the gene that codes for its production. It is one of many human leucocyte antigens (HLA). Human leucocyte antigens are a group of proteins that help the body's immune system identify its own cells and distinguish between "self" and "non-self." Everyone has an inherited combination of HLA genes that code for the antigens present on the surface of white blood cells (leucocytes) and other cells that contain a nucleus. While not as unique as a fingerprint, the presence or absence of each antigen creates a distinctive HLA combination for each person. This test determines the presence or absence of human leucocyte antigen B27 (HLA-B27) on the surface of a person's white blood cells.
HLA-B27 is found in about 8% of the UK population. Its presence has been associated with several autoimmune disorders. The most common of these disorders is ankylosing spondylitis (AS). In the UK approximately 95% of those with AS are positive for HLA-B27. Other disorders that have an association with the presence of HLA-B27 include juvenile rheumatoid arthritis (JRA), reactive arthritis (of which one subset is Reiter syndrome), and isolated acute anterior uveitis. Though the presence of HLA-B27 supports the diagnosis of these conditions, the relationship between HLA-B27 and the mechanism by which the diseases occur remains to be determined.
HLA-B27 may also be present in people with spondylitis associated with inflammatory bowel disease and psoriatic arthritis. While HLA-B27 has not been established as a cause of these disorders, there is a higher prevalence of the antigen in those affected.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
The HLA-B27 test is primarily requested to help strengthen or confirm a suspected diagnosis of ankylosing spondylitis (AS), reactive arthritis, juvenile rheumatoid arthritis (JRA), or sometimes anterior uveitis . The HLA-B27 test is not a definitive test that can be used to diagnose or rule out a disorder. It is used as one piece of evidence amongst others like signs, symptoms, and lab tests to support or rule out the diagnosis of certain autoimmune disorders, such as AS and reactive arthritis.
AS is chronic, progressive conditions that occur more frequently in men than women. The first symptoms typically occur between teenage years and early 30's. Often, the initial symptoms of these autoimmune disorders are subtle and may take several years before characteristic degenerative changes to bones and joints are visible on X-rays.
- Ankylosing spondylitis is characterised by pain, inflammation, and a gradual stiffening of the spine, neck and chest.
- Reactive arthritis is a group of symptoms that includes inflammation of the joints, urethra, eyes, and skin lesions.
- Juvenile rheumatoid arthritis is a form of arthritis that occurs in children.
- Anterior uveitis is associated with recurring inflammation of the structures of one or both eyes.
The HLA-B27 test may be requested as part of a group of tests used to diagnose and evaluate conditions causing arthritis-like chronic joint pain, stiffness, and inflammation. This group of tests may include an RF (rheumatoid factor) with an ESR (erythrocyte sedimentation rate) and a CRP (C-Reactive protein). HLA-B27 is sometimes used to help evaluate someone with recurrent uveitis that is not caused by a recognisable disease process.
When is it ordered?
An HLA-B27 test may be requested when a person has acute or chronic pain and inflammation in the spine, neck, chest, eyes, and/or joints, and the doctor suspects an autoimmune disorder that is associated with the presence of HLA-B27. Doctors frequently must rely on their clinical findings and the HLA-B27 test result when diagnosing ankylosing spondylitis, and other HLA-B27-related disorders, because the characteristic changes to the bones may not be detectable for several years. Under these circumstances, HLA-B27 is not diagnostic but adds additional information, increasing or decreasing the likelihood that the patient has ankylosing spondylitis. An HLA-B27 may also be ordered when someone has recurrent uveitis.
What does the test result mean?
If a person is positive for HLA-B27 and has symptoms such as chronic pain, inflammation, and/ or consequent damage to the spine and joints (as seen on X-ray, or other imaging), then it supports a diagnosis of ankylosing spondylitis, reactive arthritis, or another autoimmune disorder that is associated with the presence of HLA-B27. This is especially true if the person is young, male, and if he experienced his first symptoms before the age of 40.
If HLA-B27 is negative, then it is less likely that the symptoms are due to an HLA-B27 associated autoimmune disorder . This does not, however, mean that the person does not have the suspected condition, as a certain percentage of people with each disorder will be HLA-B27 negative.
- Ankylosing spondylitis: about 95% are HLA-B27 positive, and 5% are HLA-B27 negative
- Juvenile rheumatoid arthritis (JRA): about 80% are HLA-B27 positive
- Reactive arthritis: about 60-85% are HLA-B27 positive
- Isolated acute anterior uveitis: about 40-70% are HLA-B27 positive
Whether or not HLA antigens will be present is genetically determined. Their production is controlled by genes that are passed from parents to children. If a person has a close family member with an HLA-B27 related disease that affects the joints of the spine (AS or other related condition) and is positive for the HLA-B27 antigen, then that person is at an increased risk of developing a similar disease.
Is there anything else I should know?
Although the diseases associated with HLA-B27 occur more frequently in men, women can also be affected. The signs and symptoms of the diseases associated with HLA-B27 are often milder in women than in men.
With new genetic testing methods, it is now possible to separate HLA-B27 into subtypes. So far, about fifteen different subtypes have been identified. The most common in the U.S. are HLA B27*05 and HLA B27*02. How the presence of these specific subtypes affects the likelihood of developing an autoimmune disease is not yet known.
What causes the autoimmune disorders associated with HLA-B27?
In most cases, the cause is not known. However, in some cases of reactive arthritis, there is an association between a previous infection by a microorganism, such as Chlamydia, Campylobacter, Salmonella, Ureaplasma, or Yersinia, and the beginning of the disease. It is thought that similarities between the HLA-B27 antigen and the antigens found on the surface of the microorganisms trigger the immune system to fight both the microorganism and the person's own tissues, launching the autoimmune disorder after the resolution of the infection.
Can I be tested for HLA-B27 in my doctor's office?
HLA-B27 testing requires specialized equipment and expertise to perform. It is not typically performed in a doctor's office and is not offered by every laboratory. In most cases, your blood sample will be sent to a reference laboratory.
Should everyone have an HLA-B27 test done?
Routine testing of the general public is not recommended. Usually only those with symptoms should be tested. A positive HLA-B27 in a person who does not have symptoms or a family history of HLA-B27-associated disease is not clinically significant. It does not help predict the likelihood of developing an autoimmune disease. Occasionally a family member of a person who is positive for HLA-B27 and has an autoimmune disorder may be tested, but the test result cannot be used to predict whether the tested person will develop a related autoimmune disease.