Explanation of HLA B27 Blood Test Results


The HLA-B27 blood test is used with a series of other tests to determine if there is an autoimmune disorder present that could be affecting the body. It isn’t a definitive test, but is often used to determine if there is reactive arthritis or juvenile rheumatoid arthritis that needs to be addressed. It is also used to confirm or strength a diagnosis of AS or anterior uveitis. Outside of juvenile rheumatoid arthritis, the symptoms that would lead a medical provider to order this test can start as early as 30 years of age.

If there is pain and inflammation in the neck and chest with a gradual stiffing of the spine, swelling of the joints with lesions on the skin, or inflammation of the eyes, the HLA-B27 blood test can be used to help determine the cause of the bothersome physical symptoms. This is because it detects the Human Leukocyte Antigen B27.

What Do My Test Results Mean?

If your HLA-B27 blood test has come back as positive, then the test results will be compared to the physical symptoms that are being experienced. If there is chronic inflammation present, pain, or changes to the bones that are degenerative in nature, then this will support a diagnosis of one of the associated conditions. Men under the age of 40 are the most common demographic to see a positive test result from these bothersome physical symptoms.

If the HLA-B27 blood test comes back as negative, then it means the test results were unable to detect the presence of this specific marker. Just because a test is negative, however, doesn’t mean that one of the conditions listed on this page are not present. Sometimes people who do not have this specific antigen can develop these autoimmune disorders. It is also possible that a positive test can be false because the marker is present, but the autoimmune disorder never develops.

Some people have genetic determinations as to whether or not they may test with a false positive or a false negative. Anyone who has the HLA-B27 marker is at a higher overall risk than the general population of developing the diseases and disorders that are being evaluated.

Here’s What You Need to Know

Although men under the age of 40 are the most common demographic for testing and positive results with the blood test, it can affect anyone. In women, the symptoms of these autoimmune disorders tend to be less severe, so it could be that more women have an active disease, but are not seeking treatment options for it.

There are also genetic tests available today that can separate the subtypes of the HLA-B27 marker. Researchers have found more than 70 different subtypes so far and work is ongoing. How these subtypes relate to risk assessments for disease, however, is not yet known.

For some individuals, the HLA-B27 marker lies dormant until it has been triggered by something. Certain microorganisms, such as salmonella or chlamydiua, have been known to create the onset of an autoimmune disorder as a side effect of the infection when this marker is present. It is believed that this happens because the microorganisms and the marker are similar enough in structure that it fools the body into attacking itself.

Most local laboratories cannot process this test. After a blood sample is taken, it will usually be sent to a reference laboratory for results. This can create a several day delay in knowing what the test results will be.

Not Everyone Should Have the HLA-B27 Blood Test

Because of the genetic nature of this blood test, it is not recommended for the general public to receive it as a screening tool. It should only be ordered when there are enough symptoms present that justify using it. Someone can be positive with the HLA-B27 blood test, have a family history of diseases associated with the marker, and still have results that are medically insignificant

The HLA-B27 blood test results cannot be used to determine whether or not an individual with develop an autoimmune disorder. It can only be used to determine the likelihood that an autoimmune disorder has developed when combined with additional testing.

If there are the symptoms of arthritis bothering you or you have chronic stiffness, pain, or inflammation, then consider speaking with your doctor about the pros and cons of having the HLA-B27 blood test. Use this guide to ask questions about your specific medical history and what the results from the test may mean for you.