HLA-B27 Test – What It Measures, How It’s Done & What Results Mean

What is the HLA-B27 Test?

The HLA-B27 test is a specialised blood test that detects the presence of the human leukocyte antigen B27 (HLA-B27) gene or surface protein on white blood cells. This protein is part of the major histocompatibility complex (MHC) class I family, which helps your immune system distinguish between self and non-self cells.

The HLA-B27 blood test is particularly valuable because This antigen is found in about 6–9% of the global population, with variations across ethnic and geographic groups, but its presence significantly increases your risk of developing certain inflammatory conditions, like ankylosing spondylitis or reactive arthritis.

However, it's crucial to understand that this test serves as a risk indicator rather than a definitive diagnostic tool for any specific condition.

Why is the HLA-B27 Test Done?

Healthcare providers recommend the HLA-B27 test for several important reasons:

• To support the diagnosis of ankylosing spondylitis in patients experiencing chronic back pain and stiffness
• To investigate cases of reactive arthritis following infections
• To evaluate unexplained anterior uveitis (eye inflammation)
• To assist in diagnosing inflammatory bowel disease-associated arthritis
• To provide additional information when Juvenile idiopathic arthritis (JIA) is suspected
• To help determine the underlying cause of persistent joint pain or inflammation

The test is particularly useful when patients present with symptoms suggestive of spondyloarthropathies, as it can help narrow down potential diagnoses and guide treatment decisions.

Conditions Linked to HLA-B27 Positive Results

Several autoimmune disorders show strong associations with positive HLA-B27 test results:

• Ankylosing spondylitis: Affecting the spine and sacroiliac joints
• Reactive arthritis: Developing after certain infections
• Psoriatic arthritis: Occurring alongside the psoriasis skin condition
• Juvenile idiopathic arthritis (JIA): Particularly in young patients
• Anterior uveitis: Causing eye inflammation and vision problems
• Inflammatory bowel disease-associated arthritis: Linked to Crohn's disease
• Undifferentiated spondyloarthropathy: Early-stage inflammatory arthritis

Research indicates that approximately 50–70% of patients with ankylosing spondylitis and 50% of those with reactive arthritis carry the HLA-B27 antigen, while associations in psoriatic arthritis and IBD are less frequent (20–50%), making this test particularly valuable for arthritis diagnosis in this condition.

Who Should Get an HLA-B27 Test?

The HLA-B27 test is recommended for individuals experiencing specific symptoms or circumstances that suggest possible spondyloarthropathy. Healthcare providers typically consider this test when patients present with chronic inflammatory symptoms that may indicate an autoimmune disorder.

Key situations warranting HLA-B27 antigen test consideration include:

• Persistent, unexplained back pain and stiffness, especially in individuals under 45
• Recurrent eye inflammation episodes requiring medical treatment
• Family history of ankylosing spondylitis or related inflammatory conditions
• Joint pain accompanied by inflammatory bowel symptoms
• Arthritis symptoms occurring alongside psoriasis or other skin conditions

How the HLA-B27 Gene Works (Simple Explanation)

The HLA-B27 gene helps your body make a protein that sits on your white blood cells. This protein works like a security guard, showing “ID cards” of germs to your immune system so it knows what to attack.

For most people, this system works smoothly. But if you carry the HLA-B27 type, your immune system can sometimes get confused and mistake your own healthy tissues—like your joints, spine, or eyes—for harmful invaders. This mix-up can lead to inflammation and certain autoimmune problems.

An HLA-B27 test simply tells you whether you have this gene type, which can increase your chances of developing these conditions.

Procedure: How the HLA-B27 Test is Done

The HLA-B27 test procedure follows these straightforward steps:

1. Preparation: Your healthcare provider cleans the skin over a vein in your arm with an antiseptic.
2. Tourniquet application: A tight band is wrapped around your upper arm to make the veins more visible.
3. Blood collection: A sterile needle is inserted into the vein to draw blood into collection tubes.
4. Sample processing: The blood sample is labelled and sent to the laboratory for analysis.
5. Laboratory testing: Technicians use Flow cytometry (antigen detection) or PCR-based molecular testing (gene detection) to detect HLA-B27.
6. Result reporting: HLA-B27 test results are typically available within 24–48 hours, depending on the laboratory method used.

Preparation for the HLA-B27 Test

• No fasting or dietary restrictions are required before the test
• Continue taking your regular medications unless specifically advised otherwise
• Wear comfortable clothing that allows easy access to your arm
• Inform your healthcare provider about any medications or supplements you're taking
• Stay well-hydrated before your appointment to make blood collection easier

Understanding HLA-B27 Test Results

The HLA-B27 test normal range is straightforward; it indicates either "positive" or "negative" for the presence of this antigen. A positive HLA-B27 test result means the antigen was detected in your blood sample, indicating a higher statistical risk of developing certain autoimmune disorders. However, this doesn't guarantee you'll develop any specific condition.

Conversely, a negative result means the antigen wasn't found, which significantly reduces your likelihood of developing HLA-B27-associated diseases. Borderline or equivocal results may require repeat or confirmatory molecular testing to exclude cross-reactivity or technical error.

What Does a Positive HLA-B27 Result Mean?

A positive HLA-B27 test result indicates you carry the genetic marker associated with increased risk for spondyloarthropathies and related autoimmune disorders. However, it's essential to understand that carrying this antigen doesn't mean you have or will definitely develop these conditions.

Can You Have HLA-B27 and No Disease?

Absolutely. Most people who test positive for HLA-B27 never develop any associated autoimmune disorders. Research shows that only about 1-5% of HLA-B27-positive individuals actually develop ankylosing spondylitis, despite over 90% of patients with this condition carrying the antigen.

This means that having a positive HLA-B27 test result simply places you in a higher-risk category rather than predicting inevitable disease development. Many factors influence whether someone with HLA-B27 develops symptoms, including additional genetic variants, environmental triggers, infections, and lifestyle factors.

When HLA-B27 Results May Be Misleading (False Positives/Negatives)

Several factors can affect the accuracy of your HLA-B27 antigen test:

• Cross-reactivity: Structural similarity between HLA-B27 and HLA-B7 antigens can occasionally produce false-positive results in flow cytometry assays
• Technical limitations: Laboratory errors or equipment issues may affect accuracy
• Ethnic variations: HLA-B27 prevalence differs significantly across populations
• Disease variability: Some patients with spondyloarthropathies test negative for HLA-B27
• Borderline results: Values near the detection threshold may require confirmatory testing

HLA-B27 vs ANA, ESR, and CRP Tests (Comparison)

• HLA-B27 test: Identifies genetic predisposition to specific inflammatory conditions
• ANA (Antinuclear Antibody): Screens for systemic autoimmune diseases like lupus
• ESR (Erythrocyte Sedimentation Rate): Measures general inflammation levels in your body
• CRP (C-Reactive Protein): Detects acute inflammatory responses

While the HLA-B27 blood test reveals genetic susceptibility, ESR and CRP tests indicate active inflammation occurring right now. Your healthcare provider may order multiple tests to build a complete picture of your condition.

Benefits of the HLA-B27 Test

• Helps support diagnosis in chronic inflammatory back pain when combined with clinical findings and imaging
• Supports early diagnosis of spondyloarthropathies when combined with clinical symptoms
• Guides healthcare providers toward appropriate specialist referrals
• Helps assess familial predisposition in cases where hereditary spondyloarthropathies are suspected
• Assists in developing personalised monitoring and treatment strategies

Risks or Side Effects of the HLA-B27 Test

The HLA-B27 test procedure carries minimal risks typical of routine blood draws:

• Mild discomfort or brief pain at the needle insertion site
• Small bruise or slight swelling where the needle entered
• Very rare risk of infection at the puncture site
• Occasional mild dizziness or fainting during blood collection, especially in sensitive individuals

When to Follow Up With a Doctor After HLA-B27 Results

Contact your healthcare provider promptly in these situations:

• Your HLA-B27 test result is positive, and you're experiencing joint, back, or eye symptoms
• New or worsening symptoms develop after receiving your results
• You have questions about your risk or need clarification about your results
• A family history of autoimmune disorders combined with concerning symptoms warrants discussion
• You require referral to a rheumatologist or other specialist for further evaluation

Conclusion

Understanding your HLA-B27 test result empowers you to make informed decisions about your health monitoring and treatment options. Whether your result is positive or negative, maintaining open communication with your healthcare provider ensures you receive appropriate care tailored to your individual circumstances.

At Metropolis Healthcare, we understand the importance of accurate diagnostic testing in managing your health journey. Our comprehensive network of over 220 laboratories and 4,600 service centres ensures reliable HLA-B27 testing with precise results you can trust. Through our convenient home sample collection service, spanning 10,000+ touchpoints across India, you can access essential diagnostic tests from the comfort of your home.

With our advanced testing capabilities and commitment to accuracy, we're here to support your health decisions with dependable results and compassionate care. Take the first step toward better health management by booking your diagnostic tests today.

FAQs

What does the HLA-B27 test detect?

The HLA-B27 test detects the presence of a specific protein called human leukocyte antigen B27 on your white blood cells. This genetic marker is associated with an increased risk of developing certain autoimmune disorders, particularly inflammatory arthritis conditions such as ankylosing spondylitis and reactive arthritis.

Is HLA-B27 an autoimmune disease?

No, HLA-B27 is not a disease itself but rather a genetic trait that increases your susceptibility to developing certain autoimmune disorders. It's a normal protein variant that some people inherit, but its presence can influence how your immune system responds to various triggers.

Can HLA-B27 be cured?

HLA-B27 cannot be "cured" because it's a genetic characteristic you're born with, similar to your eye colour or blood type. However, if you develop HLA-B27-associated conditions, these can often be effectively managed with appropriate medical treatment and lifestyle modifications.

What are the symptoms of HLA-B27-positive individuals?

Most people who test positive for HLA-B27 experience no symptoms whatsoever and remain healthy throughout their lives. However, if autoimmune disorders do develop, symptoms might include chronic back pain, joint stiffness, eye inflammation, or skin problems, depending on the specific condition.

How accurate is the HLA-B27 test?

The HLA-B27 test is highly accurate when performed using modern laboratory techniques like flow cytometry. However, rare cross-reactions with similar proteins can occasionally cause false positive results, which is why borderline results may require confirmatory testing using molecular methods.

Is HLA-B27 genetic?

Yes, HLA-B27 is inherited from your parents through your genes. If one parent carries HLA-B27, you have approximately a 50% chance of inheriting it. However, inheriting the gene doesn't guarantee you'll develop any associated health conditions.

Can stress or infection affect HLA-B27 results?

Stress and infections cannot change your HLA-B27 test result because this marker reflects your genetic makeup rather than temporary physiological changes. However, infections and stress may potentially trigger the development of HLA-B27-associated conditions in genetically susceptible individuals.

Does HLA-B27 mean ankylosing spondylitis?

A positive HLA-B27 result does not mean you have ankylosing spondylitis. While over 90% of people with ankylosing spondylitis carry HLA-B27, only 1-5% of HLA-B27-positive individuals actually develop this condition. The test indicates increased risk, not confirmed disease.

Can you test positive for HLA-B27 and stay healthy?

Absolutely. The vast majority of people who test positive for HLA-B27 remain completely healthy and never develop any associated autoimmune disorders. Having this genetic marker simply means you should be aware of potential symptoms and maintain regular healthcare monitoring.