Blood test
HLA-B27 test
HLA-B27 test: what it measures, why a doctor orders it, how to prepare, and what a high or low result can mean - with private and NHS access routes in the UK.
Key facts
At a glance
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What it measures: whether you carry the HLA-B27 tissue type, a genetic marker linked to axial spondyloarthritis and related conditions.
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Why it is ordered: when inflammatory back pain, uveitis or reactive arthritis raises the possibility of spondyloarthritis.
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No fasting or special preparation is needed for this test on its own.
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Reference ranges: this is a genetic result that never changes, and most carriers never develop disease - several percent of the UK population are positive. Every laboratory publishes its own interval, so the range printed on your report is the one that applies to you.
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A raised result or positive result raises the likelihood of axial spondyloarthritis when symptoms and imaging point the same way, but proves nothing alone. A low result or negative result makes ankylosing spondylitis considerably less likely without excluding it.
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Results typically take a few days to two weeks, because the sample is analysed in batches at a specialist laboratory.
The full picture
What this test tells you, and how to get it
The HLA-B27 test measures whether you carry the HLA-B27 tissue type, a genetic marker linked to axial spondyloarthritis and related conditions. Doctors most often request it when inflammatory back pain, uveitis or reactive arthritis raises the possibility of spondyloarthritis. No fasting or special preparation is needed for this test on its own. This is a genetic result that never changes, and most carriers never develop disease - several percent of the UK population are positive, and reference intervals genuinely differ between laboratories, so no single number should be treated as a universal cut-off - your result is always read against the range printed on your own report. Broadly, a raised result or positive result raises the likelihood of axial spondyloarthritis when symptoms and imaging point the same way, but proves nothing alone, while a low result or negative result makes ankylosing spondylitis considerably less likely without excluding it, and either finding is interpreted alongside your symptoms, medication and other results rather than in isolation. Results typically take a few days to two weeks, because the sample is analysed in batches at a specialist laboratory.
In the UK there are two routes to this test. Your NHS GP can arrange it free of charge when it is clinically indicated, though getting the appointment, the blood draw and the follow-up discussion can add days to weeks depending on local demand. Privately, the HLA-B27 test can usually be booked within days - through a private GP, a walk-in phlebotomy clinic or a self-request home-testing service - usually requested by a rheumatologist alongside MRI of the sacroiliac joints. A private result still deserves a clinician's interpretation: an isolated number without context is where most confusion about blood tests begins.
A quiet reminder
This guide is for information, not medical advice.
Your own clinician knows your history and can tell you which parts apply to you. Reference ranges vary between laboratories - always read your result against the interval printed on your own report. Next review of this page: 2027-09-27.
Frequently asked
Common questions about HLA-B27 test.
Quick, plain-English answers to what people ask us most.
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What is the HLA-B27 test?
The HLA-B27 test is a blood test that checks whether you carry the HLA-B27 gene variant, which is more common in people with certain inflammatory joint and eye conditions, though having the gene does not mean you definitely have or will develop such a condition.
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Why would a doctor order this test?
It is commonly used to help support a diagnosis of ankylosing spondylitis, reactive arthritis, or certain forms of uveitis (eye inflammation), particularly when symptoms such as persistent lower back pain or joint stiffness are present in a younger adult.
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Do I need to prepare for the HLA-B27 test?
No fasting or special preparation is required; it is a routine blood test.
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What happens during the test?
A blood sample is taken from a vein in your arm and sent to a specialist laboratory for genetic analysis.
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Does the test hurt, and are there any risks?
It involves the same minor discomfort as any blood test, such as a brief pinch and possible small bruise. There are no significant risks beyond those of a standard blood draw.
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How long do results take?
Results typically take around one to two weeks, as it requires specialised laboratory processing.
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What does a positive result mean, and what happens next?
A positive result raises the likelihood that certain symptoms relate to an inflammatory condition, but it is not diagnostic on its own, since many people with the gene never develop symptoms. Your doctor will combine this result with your symptoms, examination, and imaging to reach a diagnosis and discuss appropriate next steps.
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How much does the HLA-B27 test cost privately, and is it on the NHS?
It is available on the NHS when clinically indicated, though specialist rheumatology review may involve a wait. Private testing is available, usually with a specialist consultation included, and cost varies by provider.
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Is the HLA-B27 test accurate?
The test reliably detects whether the gene is present, but a positive or negative result must always be interpreted alongside your symptoms and other findings, since the gene alone does not confirm or exclude a diagnosis.
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How do I book HLA-B27 testing privately, and how quickly can I be seen?
You can book directly with a private clinic offering rheumatology assessment, often with an appointment available within a week or two, giving a faster route to specialist input if symptoms are troubling you.