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, an antigen, or protein, found on the surface of infection-fighting
white blood cells. If you have HLA-B27, you may have an autoimmune disease. Autoimmune
diseases occur when your immune system sees its own cells as foreign invaders and
destroys them. The most common autoimmune disorders associated with HLA-B27 antigens
Ankylosing spondylitis, a form of arthritis that affects the spine
Juvenile arthritis, which occurs in children
Reactive arthritis, or Reiter's syndrome, a type of arthritis in the joints
Your HLA antigens are unique to you and are determined by your genes. Therefore this
blood test is useful in paternity investigations.
Why do I need this test?
You might have this test if your healthcare provider suspects that you have ankylosing
spondylitis because of pain and stiffness in your back, neck, or chest. This is especially
true if you are a man and have symptoms in your early 30s.
You also might have this test if you are having an organ transplant of your kidney
or bone marrow, for instance. Your donor's HLA antigens must match yours for the transplant
to have a chance to be successful. You might have this test if someone needs to determine
What other tests might I have along with this test?
Your healthcare provider also might order:
Erythrocyte sedimentation rate, or ESR, which suggests inflammation
C-reactive protein, which also can look for inflammation
Joint X-rays or MRI
These tests can help confirm an autoimmune diagnosis if your HLA-B27 antigen test
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even if your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
Normal results are negative, which means you don't have HLA-B27 in your blood. A positive
test means HLA-B27 was found in your blood. You may have a higher-than-average risk
of developing or having 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 than if you are of a different race.
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 requires a blood sample, which is drawn through a needle from a vein in your
Does this test pose any risks?
Taking a blood sample with a needle carries risks that include bleeding, infection,
bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight
stinging sensation or pain. Afterward, the site may be slightly 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 illicit drugs you may use.