Does this test have other names?
Human lymphocyte antigen B27, human leukocyte A antigen, white blood cell antigens,
histocompatibility leukocyte A antigen
What is this test?
This test looks for HLA-B27, which are proteins called antigens. These are found on
the surface of white blood cells that are fighting infection. If you have HLA-B27,
you may have an autoimmune disease. An autoimmune disease is when your immune system
attacks your own cells. The most common autoimmune disorders connected with HLA-B27
Ankylosing spondylitis, a form of arthritis that affects the spine
Juvenile arthritis, which occurs in children
Reactive arthritis, a type of arthritis in the joints
Your HLA antigens are unique to you. They are determined by your genes. Because of
that, this blood test is also useful as a paternity test.
Why do I need this test?
You may need this test if your healthcare provider thinks that you have ankylosing
spondylitis. This can cause pain and stiffness in your back, neck, or chest. This
is more common if you are a man and have symptoms in your early 30s.
You also may need this test if you are having an organ or tissue transplant. For example,
this may be a donor kidney or bone marrow. Your donor's HLA antigens must match yours
for the transplant to have a chance to be successful.
Or a man may have this test to determine if he is the father of a child.
What other tests might I have along with this test?
If your HLA-B27 antigen test is positive, you may need other tests to help confirm
a diagnosis of an autoimmune disease. You may have tests such as:
Erythrocyte sedimentation rate (ESR) which may mean you have inflammation
C-reactive protein, which also can look for inflammation
Joint X-rays or MRI
What do my test results mean?
Test results may vary depending on your age, gender, health history, the method used
for the test, and other things. Your test results may not mean you have a problem.
Ask your healthcare provider what your test results mean for you.
A negative result mean you don't have HLA-B27 in your blood. A positive result means
HLA-B27 was found in your blood. You may have a higher-than-average risk of certain
autoimmune diseases, such as ankylosing spondylitis and reactive arthritis. If you
are white, you are more likely to test positive for the HLA-B27 antigens.
If you need an organ or tissue transplant and your HLA antigens are not compatible
with those of your donor, your body could reject the transplant.
In a paternity case, if the child or father has an unusual HLA genotype, paternity
could be clear. If it's a common HLA genotype, the child could have many potential
How is this test done?
The test is done with a blood sample. A needle is used to draw blood from a vein in
your arm or hand.
Does this test pose any risks?
Having a blood test with a needle carries some risks. These include bleeding, infection,
bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may
feel a slight sting or pain. Afterward, the site may be sore.
What might affect my test results?
No other factors can affect your results.
How do I get ready for this test?
You don't need to prepare for this test. But be sure your healthcare provider knows
about all medicines, herbs, vitamins, and supplements you are taking. This includes
medicines that don't need a prescription and any illegal drugs you may use.