Glossary
HLA-B27
One test result gets treated as a verdict, and it isn't one. What it's worth depends heavily on where your family came from, which is not something most people are told when the blood is drawn. That's the whole of this page, and the rest is the evidence for it.
What the research found.
One study in Lebanon typed 141 patients with axial spondyloarthritis and 106 blood donors. The marker was present in 41.1 percent of the patients and in 3.8 percent of the donors. As a test it cleared 96.2 percent of the donors, and a positive result came with a likelihood ratio of 10.9.
One study of 925 people with ankylosing spondylitis measured how often the marker turned up by ancestry. It was found in 85.3 percent of White patients and in 86.7 percent of Latino patients, while among Black patients it was 62.5 percent. That spread is why the test performs differently in different places.
One study looked at 407480 UK Biobank participants of European ancestry. Having the marker wasn't linked to any change in death rate, at a hazard ratio of 1 from 0.97 to 1.1 and a P value of 0.349. Deaths from blood vessel disease showed no rise either.
One study compared this single marker against a score built from many genes at once, on one set of patients. For telling ankylosing spondylitis from healthy controls, the marker alone scored 0.869 while the many-gene score reached 0.924. Sacroiliac scanning scored 0.885 on that comparison and C-reactive protein managed 0.700.
What this test is
HLA-B27 is one form of a gene, and the gene family it belongs to has a job worth knowing about. It helps your immune system tell your own cells from things that don't belong there. Everybody has genes in that family, and this particular form turns up more often in people with spondyloarthritis than in people without.
An ordinary blood test finds it, which is part of why it gets ordered so readily. Here is the part that trips almost everybody up at first. Having this form is fairly common and developing one of these diseases is not, and putting those two facts together is what shows you why a result on its own settles very little.
What a positive result is worth
A positive result moves the odds without closing the question, and that difference is the whole of this page. One study in Lebanon typed 141 patients with axial spondyloarthritis alongside 106 blood donors. The marker was found in 41.1 percent of the patients and in 3.8 percent of the donors, so as a test it cleared 96.2 percent of the donors and a positive came with a likelihood ratio of 10.9.
A likelihood ratio of 10.9 is a genuine move and it isn't a verdict. It takes whatever chance your doctor started with and raises it. If that starting chance was low, a positive result leaves it moderate rather than certain, which is a different place to be standing than most people imagine.
What a negative result is worth
Less than most people assume, and this is where the test gets over-read. It happens often enough to be worth a section of its own. In that Lebanese study, only 41.1 percent of the patients had the marker, so well over half of the people who genuinely had the disease tested negative.
Its negative predictive value there was 55.13 percent, which is barely better than a coin toss. One Moroccan study makes the point harder still. Among 136 patients with spondyloarthritis, just 7 tested positive, so almost every one of those people had a negative test and the disease anyway.
Why ancestry changes what it means
The marker is much commoner in some groups than in others, and that holds among the healthy and the ill alike. One result therefore means different things for different people. That isn't a technicality, and it's the single most practical thing on this page.
One study of 925 people with ankylosing spondylitis measured it directly. The marker was present in 85.3 percent of White patients and in 86.7 percent of Latino patients, while among Black patients it was 62.5 percent. Put those beside the Moroccan and Lebanese numbers and the gap gets wide.
A negative result is fairly reassuring where nearly nine in ten patients test positive. It tells you almost nothing where four in ten do. So it's fair to ask your doctor what a negative means for somebody with your background, which is a different question from what it means in general.
Having it without being ill
Most people with the marker never develop a rheumatic disease, and one study puts a number on what that costs them. The answer turns out to be nothing at all. It looked at 407480 UK Biobank participants of European ancestry, and having the marker made no difference to death rate, at a hazard ratio of 1 with the true value from 0.97 to 1.1 and a P value of 0.349.
No rise in deaths from blood vessel disease appeared either. That paper does report a raised death rate elsewhere, and it's worth keeping the two apart. People with established ankylosing spondylitis had a standardized mortality ratio of 1.37, from 1.11 to 1.62, and that belongs to having the disease rather than to the marker itself.
One more finding from that paper is worth knowing about. Some people with axial spondyloarthritis have no damage showing on x-ray. Their death rate came in below the general population, at 0.44 from 0.23 to 0.77, which is not a result anybody expected.
It isn't the only gene involved
This marker is the famous one and it isn't the whole picture. Several genes are involved in these diseases and this happens to be the one with a name people recognize. One study built a score from many genes at once and set it against the single marker.
For the job of telling ankylosing spondylitis from healthy controls, the many-gene score reached 0.924 while the marker on its own reached 0.869. Sacroiliac scanning reached 0.885 and C-reactive protein reached 0.700. So the marker holds its own without leading the field, which is a fair summary of where it sits.
The predictive figures make the difference concrete, so start from a one-in-ten chance. That's roughly where somebody under 45 with long-standing back pain sits before any test is run. From there the many-gene score reached a positive predictive value of 78.2 percent and a negative predictive value of 100 percent, while the single marker managed 51.9 percent and 97.9 percent.
A separate study followed 1075 patients and found two other markers in this gene family turning up slightly more often in one group. That group had joint swelling outside the spine as well. Both links were marginal and neither one is in routine use, so nobody is going to test you for them.
What differs between positives and negatives
One large study typed 2269 people with axial spondyloarthritis across 24 countries, of whom 1753 had the marker and 516 did not. The two groups looked different in ways worth knowing about. Those with the marker were more often men, at 72.1 percent against 54.3 percent, and they had a family history more often, at 29.8 percent against 15.3 percent. They were diagnosed younger too, at a mean of 31.6 years against 37.7 years.
Those without it more often had features outside the spine. Joint swelling elsewhere appeared in 47.5 percent against 42.1 percent, and psoriasis in 19.4 percent against 10.2 percent. Tender tendon attachments ran 56.6 against 49.8 percent, and bowel disease ran 12.8 against 3.4. The bowel figure is the one that stands out from that list, because it runs at nearly four times the rate of the positives, and it's the clearest hint that the two groups don't line up neatly.
None of that changes what you're offered in the clinic. It does mean one thing worth holding onto. Somebody who tests negative may have a slightly different-looking illness rather than no illness at all.
The eye link
This marker does predict one thing well, and that thing is a particular eye problem. Inflammation at the front of the eye is the commonest thing spondyloarthritis does outside the joints, and it's worth knowing the signs. One study followed 301 people with spondyloarthritis, and 82 of them had at least one episode, with prevalence at 11.5 percent at the point of diagnosis rising to 39.3 percent twenty years later.
Having the marker was independently linked to it, at a hazard ratio of 4.5 with the true value from 1.3 to 15.2. That range is wide, so hold the size of it loosely, though the direction is beyond doubt. The practical part counts for more than the figure does.
Sudden eye pain, redness, or blurred vision needs seeing the same day, and so does new trouble with bright light. That isn't something to save for your next appointment. It's the one piece of this page that has a deadline attached, and it's the piece worth remembering if you forget the rest.
Common misconceptions.
Myth. A positive result means I have the disease.
Reality. It doesn't, and most people who have this marker never develop a rheumatic disease at all. What a positive does is raise the odds, and in one study it came with a likelihood ratio of 10.9, which is a real move. Raising the odds and settling a question are two different things, and your symptoms, your exam, and your scans still do most of the work.
Myth. A negative result rules it out.
Reality. Far from it, and the numbers make that plain. In one study of 141 patients with axial spondyloarthritis, only 41.1 percent had the marker, and its negative predictive value was 55.13 percent. In one Moroccan group of 136 patients, just 7 tested positive, so a negative result leaves the question open and how far open depends on where your family came from.
Myth. Everyone with ankylosing spondylitis has it.
Reality. Most do and not all, which is a distinction worth holding. One study of 925 people with the disease found it in 85.3 percent of White patients and 86.7 percent of Latino patients, while among Black patients it was 62.5 percent. A second study split people by x-ray damage and found 82 percent among those with damage against 68 percent among those without, at a P value of 0.03.
Myth. Having it will shorten my life.
Reality. Not on the evidence here, and the study behind that is a large one. It looked at 407480 UK Biobank participants of European ancestry, and having the marker made no difference to death rate at all, at a hazard ratio of 1 from 0.97 to 1.1. The raised death rate in that paper belonged to people with established disease rather than to people who simply have the marker.
Myth. It's the only genetic thing that counts.
Reality. It's the best known one and it isn't the whole story. One study built a score from many genes at once, and that score told ankylosing spondylitis from healthy controls at 0.924, against 0.869 for this marker alone. A separate study found two other markers turning up more often in people who also had joint swelling outside the spine.
Related terms.
- Ankylosing spondylitis, the disease this marker is most linked to.
- Uveitis, the eye problem that goes with it.
- Ankylosing spondylitis questions, for what happens after a diagnosis.
Questions patients ask.
What is HLA-B27?
It's one form of a gene, and that gene helps your immune system tell your own cells from invaders. Everybody has genes in this family, and an ordinary blood test finds this one. The confusing pair of facts is that having this form is fairly common while getting ill from it is not. Most people who have it go through their whole lives without a rheumatic disease of any kind.
Does a positive result mean I have the disease?
No, because what it does is move the odds rather than settle the question. In one study, a positive result came with a likelihood ratio of 10.9, which is a real move in probability rather than a rounding error. Most people with the marker never develop a rheumatic disease of any kind. Your symptoms, your examination, and your scans count for more than this one line on a report.
Does a negative result rule it out?
No, and this is where the test gets over-read more often than anywhere else. In one study of 141 patients with axial spondyloarthritis, just 41.1 percent had the marker, which means well over half of the patients tested negative. Its negative predictive value in that group was 55.13 percent, which is close to a coin toss.
Why does ancestry change the answer?
Because the marker is much commoner in some groups than in others, and that holds among the ill and the healthy alike. One study of 925 people with ankylosing spondylitis found it in 85.3 percent of White patients, 86.7 percent of Latino patients, and 62.5 percent of Black patients. One Moroccan group of 136 patients had just 7 positives. A negative result is fairly reassuring in one of those settings and nearly worthless in another.
Should I get my children tested?
This page can't answer that one, and your own team is the place for it. What's worth knowing before you ask is that a positive in somebody with no symptoms tells you very little, because most people with the marker never become ill. A result like that can worry a healthy person for years while changing nothing anybody does. Have the conversation before the test rather than after it.
Does it change my treatment?
Not directly, on the evidence here, though the two groups do look different. One study typed 2269 patients, and those without the marker more often had joint swelling outside the spine, psoriasis, tender tendon attachments, and bowel disease. Those with it were more often men, and they were diagnosed younger, at 31.6 years against 37.7.
Does it affect my eyes?
It's linked to one eye problem, and the link is a strong one. One study followed 301 people with spondyloarthritis, and 82 of them had at least one bout of inflammation at the front of the eye. Having the marker was independently linked to that, at a hazard ratio of 4.5 from 1.3 to 15.2. Sudden eye pain, redness, or light sensitivity needs seeing the same day.
Will having it shorten my life?
On the evidence here the answer is no. One study looked at 407480 UK Biobank participants of European ancestry, and having the marker made no difference to death rate, at a hazard ratio of 1 from 0.97 to 1.1 and a P value of 0.349. That paper does report raised death rates elsewhere, and those belonged to people with established disease rather than to people who simply have the marker.
References.
- Ziade N; Abi Karam G; Merheb G et al. HLA-B27 prevalence in axial spondyloarthritis patients and in blood donors in a Lebanese population: Results from a nationwide study. Int J Rheum Dis. 2019;22:708-714. 10.1111/1756-185X.13487Nationwide study in Lebanon
- Jamalyaria F; Ward MM; Assassi S et al. Ethnicity and disease severity in ankylosing spondylitis a cross-sectional analysis of three ethnic groups. Clin Rheumatol. 2017;36:2359-2364. 10.1007/s10067-017-3767-6Cross-sectional analysis of 925 patients with ankylosing spondylitis enrolled in a longitudinal outcomes cohort
- Li Z; Khan MK; van der Linden SM et al. HLA-B27, axial spondyloarthritis and survival. Ann Rheum Dis. 2023;82:1558-1567. 10.1136/ard-2023-224434Two linked analyses
- Li Z; Wu X; Leo PJ et al. Polygenic Risk Scores have high diagnostic capacity in ankylosing spondylitis. Ann Rheum Dis. 2021;80:1168-1174. 10.1136/annrheumdis-2020-219446Development and validation of polygenic risk scores in people of European and East Asian ancestry
- Chaudhary H; López-Medina C; Khan MA et al. Clinical profile and treatment utilisation based on HLA-B*27 status in axial spondyloarthritis: results from ASAS-PerSpA study. RMD Open. 2023;9. 10.1136/rmdopen-2023-003179Journal Article
- Essouiri J; Abourazzak FE; Kona I et al. Profile of Patients with Spondyloarthritis in Morocco. Curr Rheumatol Rev. 2018;14:258-263. 10.2174/1573397113666170406125338Retrospective observational study in one Moroccan rheumatology department analysing the records of 136 patients diagnosed with spondyloarthritis between January 2009 and June 2014
- Hong C; Kwan YH; Leung YY et al. Comparison of ankylosing spondylitis and non-radiographic axial spondyloarthritis in a multi-ethnic Asian population of Singapore. Int J Rheum Dis. 2019;22:1506-1511. 10.1111/1756-185X.13603Comparative study of 262 patients with axial spondyloarthritis in a Singapore registry
- Frantz C; Portier A; Etcheto A et al. Acute anterior uveitis in spondyloarthritis: a monocentric study of 301 patients. Clin Exp Rheumatol. 2019;37:26-31. PMID 30620268Cross-sectional single-centre observational study
- Naovarat BS; Gensler L; Ward M et al. Associations of sociodemographic, clinical factors and HLA-B alleles with enthesitis and peripheral arthritis in patients with ankylosing spondylitis. RMD Open. 2025;11. 10.1136/rmdopen-2024-004589Multicentre longitudinal observational cohort of 1075 patients with ankylosing spondylitis from the Prospective Study of Outcomes in Ankylosing Spondylitis
This page gathers the published research on this subject into one place. The studies behind it were published between 1989 and 2026, and every figure links to the paper it came from. Those studies were peer reviewed. This summary of them was not. Dr. Sarah Luebker is reviewing these pages one at a time and has not reached this one yet, so it carries no medical review date and nothing here is her opinion or her advice to you. Each page gets updated as she reaches it. It is here in the meantime because the science is worth having in one organized place that is easy to find and easy to read. Talk to your own clinician before acting on any of it.