HLA-B27

A one-time test for HLA-B27, a protein on white blood cells. Many people who have it stay healthy, but it is more common in some kinds of inflammatory arthritis and eye inflammation.

AI-verified against cited sources. Awaiting expert reviewAlso called HLA-B27, B27LOINC 4821-5

What it is

HLA-B27 is a protein found on the surface of many white blood cells. It is part of how the immune system recognizes what belongs in your body. You are born with it or without it, so the result never changes. Labs check for it with a blood test, using either flow cytometry (which looks at the cells) or a DNA method called PCR. The result is reported as positive or negative. In a US national survey of adults aged 20 to 69, about 6 in 100 (6.1%) tested positive. It was more common in non-Hispanic white adults (7.5%) than in all other groups combined (3.5%).

Why it matters

A clinician may order this test when someone has long-lasting back pain that began before age 45, or repeated red, painful eye inflammation. HLA-B27 is linked to a family of inflammatory arthritis conditions called spondyloarthritis, which includes ankylosing spondylitis, reactive arthritis and psoriatic arthritis. It counts as one piece of the criteria rheumatologists use to classify axial spondyloarthritis. It cannot diagnose anything on its own. Most people with HLA-B27 never develop ankylosing spondylitis. About 5 in 100 do. At the same time, more than 8 in 10 people with ankylosing spondylitis carry HLA-B27, so a negative result does not rule these conditions out either.

If it’s high

A positive result means you carry HLA-B27. It is common, found in about 6 in 100 US adults aged 20 to 69, and it is not a diagnosis. Most people who test positive never develop ankylosing spondylitis or a related condition. HLA-B27 is more common in people with ankylosing spondylitis, reactive arthritis, psoriatic arthritis, arthritis linked to inflammatory bowel disease, and acute anterior uveitis (inflammation in the front of the eye). Your clinician reads the result together with your symptoms, exam, imaging and blood tests such as CRP.

Common causes

Inherited, and passed down in families: a parent with one copy has about a 1 in 2 chance of passing it to each child
Common in the general population: about 6 in 100 US adults aged 20 to 69, and about 8 in 100 people in the UK

What can help

Share the result with the clinician who is looking into your back pain, joint pain or eye symptoms
Ask whether seeing a rheumatologist makes sense if you have back pain that began before age 45 and has lasted three months or longer
Tell an eye doctor about the result if you get red, painful eyes

What can affect your result

The result is fixed at birth, so illness, food, medicines and time of day do not change it
Ancestry: in the US survey, non-Hispanic white adults were more than twice as likely to test positive as all other groups combined
Age: the US survey found a lower rate in adults 50 to 69 (3.6%) than in adults 20 to 49 (7.3%), which the authors say needs confirming
Lab method: flow cytometry and DNA (PCR) methods are both used
HLA-B27 is inherited, so illness, food, medicines and time of day do not change the result.
Labs use either flow cytometry (which looks at the cells) or a DNA method such as PCR, so the method named on your report can differ between labs.

Your result is fixed at birth and does not change.

When to talk to a clinician

A positive HLA-B27 result alone is not urgent. See an eye doctor promptly for a red, painful eye with sensitivity to light or blurred vision. Talk with your clinician about back pain that began before age 45 and has lasted three months or longer.

Questions you could ask

Why was this test ordered, and how will the result change what we do next?
What else, such as imaging or inflammation blood tests, would help sort out my symptoms?
How does a positive HLA-B27 fit with my symptoms?
Would a visit with a rheumatologist or an eye specialist help?
Does my family history of arthritis, back pain or eye inflammation matter here?

Questions people ask

I am HLA-B27 positive. Will I get ankylosing spondylitis?

Most likely not. About 5 in 100 people who carry HLA-B27 develop ankylosing spondylitis, according to the Johns Hopkins Arthritis Center, and the NHS notes that most people with the gene variant do not have the condition. Other genes and triggers that are not well understood also play a role. Share the result with your clinician if you have long-lasting back pain or eye inflammation.

I am HLA-B27 negative. Does that rule out these conditions?

No. More than 8 in 10 people with ankylosing spondylitis carry HLA-B27, so some people with the condition do not. The NHS also says the test is not a very reliable way to diagnose ankylosing spondylitis on its own. Clinicians look at your symptoms, exam, imaging and other blood tests too.

Do I need to repeat the test?

No. HLA-B27 is a lifelong inherited marker, so one reliable result is enough.

Show the science and sources

For clinicians and researchers

HLA-B27 is a class I HLA antigen group (HLA-B*27) that can be typed by flow cytometry or by nucleic acid amplification; LOINC has a method-independent code (4821-5) and separate codes for flow cytometry (26028-1) and NAA with probe detection (26043-0). NHANES 2009 typed HLA-B27 by PCR in 2,320 adults aged 20 to 69 (124 positive). The age-adjusted US prevalence was 6.1% (95% CI 4.6-8.2): 7.5% (5.3-10.4) in non-Hispanic white adults, 3.5% (2.5-4.8) in all other races and ethnicities combined and 4.6% (3.4-6.1) in Mexican Americans. There was no significant difference by sex (5.8% men, 6.5% women), and the prevalence was 7.3% at ages 20 to 49 versus 3.6% at ages 50 to 69 (Reveille 2012). Estimated US prevalence is 1.0 to 1.4% for axial spondyloarthritis and 0.52 to 0.55% for ankylosing spondylitis (Reveille and Weisman 2013). The ASAS classification criteria apply to people with back pain of at least three months that began before age 45: either sacroiliitis on imaging plus at least one spondyloarthritis feature, or HLA-B27 plus at least two features. In a cohort of 649 patients the full criteria had a sensitivity of 82.9% and specificity of 84.4% (Rudwaleit 2009). The prevalence of ankylosing spondylitis rises to about 5% among HLA-B27-positive people (Johns Hopkins Arthritis Center). The NHS says more than 8 in 10 people with ankylosing spondylitis carry HLA-B27, about 8 in 100 people in the UK general population carry it, most of them do not have the condition, the test is "not a very reliable method of diagnosing AS", and an estimated 5 to 10% of children who inherit the variant from a parent with AS develop it. The spondyloarthropathies are linked by their association with HLA-B27 (Kataria 2004), and acute anterior uveitis is the most common eye problem in the HLA-B27-positive spondyloarthropathies (Jhaj 2018). The evidence for HLA-B27 in everyday practice is reviewed by Lim 2018.

LOINC 4821-5 (primary), 26028-1, 26043-0. Specimen: whole-blood.

Sources

The prevalence of HLA-B27 in the US: data from the US National Health and Nutrition Examination Survey, 2009, Arthritis & Rheumatism (2012)
The epidemiology of back pain, axial spondyloarthritis and HLA-B27 in the United States, American Journal of the Medical Sciences (2013)
Ankylosing spondylitis: Causes, NHS (UK)
Ankylosing Spondylitis: Symptoms, Diagnosis and Treatment, Johns Hopkins Arthritis Center
The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part II): validation and final selection, Annals of the Rheumatic Diseases (2009)
Ocular features of the HLA-B27-positive seronegative spondyloarthropathies, Current Opinion in Ophthalmology (2018)
Spondyloarthropathies, American Family Physician (2004)
The clinical utility of human leucocyte antigen B27 in axial spondyloarthritis, Rheumatology (2018)
LOINC 4821-5, 26028-1 and 26043-0 (NLM Clinical Tables API), National Library of Medicine / Regenstrief Institute

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.