HLA B27 Test - Purpose, Procedure, Results Interpretation, Normal Values and more

The HLA B27 test is a medical diagnostic test used to determine the presence of the HLA B27 antigen on the surface of white blood cells. This genetic marker is associated with a range of autoimmune diseases, particularly those that affect the joints and spine. Although not a definitive test for disease, the HLA B27 test can provide critical information for the diagnosis and management of certain conditions, especially spondyloarthritis and other inflammatory disorders.

What is the HLA B27 Test?

The HLA B27 test is a blood test that looks for the presence of a specific antigen called HLA B27. The HLA (human leukocyte antigen) system is a part of the body’s immune system that helps recognize foreign substances. The B27 antigen is one of the many different versions of HLA found on white blood cells. A positive result for HLA B27 does not necessarily mean you have a disease, but it can indicate a higher risk of certain conditions.

The test is most commonly used to help diagnose spondyloarthritis, an umbrella term for a group of inflammatory diseases that affect the spine and joints. Conditions like ankylosing spondylitis, reactive arthritis, and psoriatic arthritis are often associated with a positive HLA B27 result.

How Does the HLA B27 Test Work?

The HLA B27 test works by detecting the presence of the HLA B27 antigen on the surface of white blood cells. The presence or absence of this antigen can provide valuable insights into the likelihood of a person developing certain autoimmune diseases. The test is typically performed through a blood sample, which is then sent to a laboratory for analysis.

The laboratory uses a technique called flow cytometry or serological testing to detect the HLA B27 antigen. In some cases, genetic testing may also be performed to identify the specific markers associated with the antigen.

When is the HLA B27 Test Performed?

The HLA B27 test is often performed when a doctor suspects an autoimmune or inflammatory condition that may be related to the presence of the HLA B27 antigen. Common reasons for ordering the test include:

• Suspected spondyloarthritis: When a patient presents with symptoms of joint pain, inflammation, and spinal issues, particularly when these symptoms appear before the age of 45.
• Inflammatory bowel disease: Conditions like Crohn’s disease or ulcerative colitis may be associated with the presence of HLA B27.
• Family history of autoimmune diseases: If someone in the family has an autoimmune or inflammatory condition linked to HLA B27, testing can help assess risk.
• Chronic back pain or stiffness: In cases of ongoing back pain that does not respond to conventional treatments, the test can help determine whether there is an underlying inflammatory cause.

Why is the HLA B27 Test Performed?

The HLA B27 test is primarily used to help diagnose autoimmune diseases, especially those that affect the joints and spine. It can provide critical information for healthcare providers, aiding in the diagnosis of conditions like:

1. Ankylosing Spondylitis (AS): Ankylosing spondylitis is a chronic inflammatory disease that primarily affects the spine, causing pain and stiffness. It is more common in young adults and often begins in the lower back. HLA B27 is found in approximately 90% of individuals with ankylosing spondylitis, making the test a useful diagnostic tool.
2. Reactive Arthritis: Reactive arthritis, also known as Reiter’s syndrome, is a form of arthritis that develops after an infection, particularly in the urinary tract, gastrointestinal system, or genital tract. The HLA B27 test is often positive in people who develop this condition, especially in those with a history of infections like chlamydia.
3. Psoriatic Arthritis: Psoriatic arthritis is an autoimmune condition that affects the joints and is associated with psoriasis (a skin condition). Some people with psoriatic arthritis also test positive for HLA B27, although the link is less strong compared to other conditions like ankylosing spondylitis.
4. Inflammatory Bowel Disease (IBD): Both Crohn’s disease and ulcerative colitis, the two main types of inflammatory bowel disease (IBD), have been associated with the HLA B27 marker. People with IBD and HLA B27 may be more likely to develop spondyloarthropathies, which are inflammatory conditions affecting the joints and spine.
5. Other Spondyloarthropathies: There are other types of spondyloarthropathies that can be associated with HLA B27, such as enteropathic arthritis, undifferentiated spondyloarthritis, and juvenile spondyloarthritis. These conditions share common characteristics like joint inflammation, especially in the lower back, hips, and large joints.

How to Prepare for the HLA B27 Test

The HLA B27 test is a relatively simple blood test, and there is generally no need for special preparation. However, there are a few things to consider before undergoing the test:

• Inform Your Healthcare Provider About Current Medications: Certain medications, particularly immunosuppressive drugs, may affect your immune system and could influence the test results. Be sure to inform your doctor about all medications you are taking, including over-the-counter supplements.
• Fasting Requirements: In most cases, fasting is not required for the HLA B27 test. However, if you are having other blood tests at the same time, your healthcare provider may ask you to fast.
• Genetic Counseling: If the test is being performed as part of a family history assessment, you may want to consider speaking with a genetic counselor. They can help you understand the implications of the results and whether other family members should be tested.
• Follow Instructions from Your Healthcare Provider: It’s always important to follow any specific instructions from your healthcare provider to ensure that the test is performed accurately and provides the most reliable results.

Test Results Interpretation

HLA B27 test results are typically reported as either positive or negative. Here’s what those results mean:

• Positive HLA B27 Test Result: A positive result means that the HLA B27 antigen was detected in your blood. However, a positive result does not necessarily mean that you have an autoimmune disease. Many people who carry HLA B27 never develop any related conditions, and the test only suggests that you may be at an increased risk for certain diseases, particularly spondyloarthropathies.
• Negative HLA B27 Test Result: A negative result means that the HLA B27 antigen was not detected in your blood. While this generally rules out many of the conditions associated with HLA B27, it does not completely exclude the possibility of having an autoimmune disease. Some people with conditions like ankylosing spondylitis may not test positive for HLA B27 but can still develop the disease.
• Interpretation in Context: It’s important to note that the HLA B27 test is not definitive on its own. The results should always be interpreted in conjunction with your medical history, symptoms, and other diagnostic tests. A positive result may lead to further testing, such as X-rays or MRI scans, to evaluate joint and spine health.

Normal Range for the HLA B27 Test

The normal range for the HLA B27 test is either positive or negative, depending on the presence of the HLA B27 antigen in your blood. A positive test result indicates the presence of the antigen, while a negative result means that the antigen was not found.

• Positive HLA B27: Suggests an increased risk of conditions like ankylosing spondylitis, reactive arthritis, and other spondyloarthropathies.
• Negative HLA B27: Rules out many of the diseases associated with HLA B27 but does not exclude the possibility of other conditions.

Uses of the HLA B27 Test

The HLA B27 test has several important uses, including:

• Diagnosing Spondyloarthropathies: The test is commonly used to diagnose conditions like ankylosing spondylitis, psoriatic arthritis, and reactive arthritis.
• Determining Risk: In individuals with symptoms suggestive of autoimmune diseases, the HLA B27 test helps determine whether the individual may be at an increased risk for specific inflammatory conditions.
• Family History Screening: If there is a family history of autoimmune diseases, the test can help identify those who are genetically predisposed.
• Monitoring Disease Progression: For those diagnosed with an HLA B27-associated condition, the test may help track disease progression and treatment effectiveness.
• Genetic Counseling: The test can assist in genetic counseling to assess the risk for developing certain diseases in family members.

10 Frequently Asked Questions About the HLA B27 Test

1. What is the HLA B27 test? The HLA B27 test is a blood test used to detect the presence of the HLA B27 antigen. This antigen is associated with a range of autoimmune diseases, particularly those affecting the joints and spine.
2. Why do I need an HLA B27 test? The HLA B27 test is used when doctors suspect conditions like ankylosing spondylitis, psoriatic arthritis, or reactive arthritis. It helps assess genetic predisposition and guide diagnosis.
3. What does a positive result mean? A positive result means that the HLA B27 antigen is present in your blood, suggesting an increased risk for conditions like ankylosing spondylitis or reactive arthritis.
4. What does a negative result mean? A negative result means that the HLA B27 antigen is not detected in your blood. While this rules out many diseases, it does not completely exclude the possibility of related autoimmune conditions.
5. How accurate is the HLA B27 test? The HLA B27 test is fairly accurate in detecting HLA B27, but it should not be relied upon alone for diagnosing diseases. The results should be considered alongside other clinical factors.
6. Do I need to prepare for the test? Preparation for the HLA B27 test is simple. No fasting is required, but it’s important to inform your doctor of any medications you are taking, as some drugs may affect the results.
7. Can I get the test if I am pregnant? Yes, the HLA B27 test can be performed during pregnancy. However, it’s essential to consult with your healthcare provider for appropriate guidance and interpretation.
8. How long does it take to get the results? Results typically take a few days to a week to be processed, depending on the testing facility.
9. Is the HLA B27 test covered by insurance? Most insurance plans cover the HLA B27 test, especially if it is deemed medically necessary to diagnose or evaluate an autoimmune condition.
10. Can I have HLA B27 and not develop disease? Yes, many people who are HLA B27-positive never develop any associated diseases. The test indicates an increased risk, but it is not a definitive predictor of disease.

Conclusion

The HLA B27 test is an essential tool in diagnosing and understanding the genetic factors associated with several autoimmune diseases and spondyloarthropathies. While a positive result may indicate a predisposition to conditions like ankylosing spondylitis and reactive arthritis, it is not a definitive diagnosis. The test is most effective when interpreted in the context of clinical symptoms, family history, and other diagnostic procedures.

If you are experiencing joint pain, stiffness, or symptoms that may suggest an autoimmune condition, speaking to your healthcare provider about the HLA B27 test can provide valuable insights into your health. With early diagnosis and appropriate management, individuals with HLA B27-associated conditions can lead healthy lives with a reduced risk of complications.