What this test measures
HLA-B27 testing detects whether you carry the HLA-B27 allele — one variant of the human leukocyte antigen (HLA) class I protein, which sits on the surface of nearly every cell and presents protein fragments to the immune system. Methods include flow cytometry, PCR, or sequence-specific probe typing. Results are simply reported as positive or negative.
HLA-B27 is present in about 6–8% of the general Indian population, but in over 90% of patients with ankylosing spondylitis (AS). It is also enriched in related spondyloarthritis conditions — reactive arthritis, psoriatic arthritis with axial involvement, juvenile spondyloarthritis, and acute anterior uveitis.
Why it matters
Ankylosing spondylitis is the prototype spondyloarthritis — a chronic inflammatory disease that causes inflammatory back pain (worse with rest, better with movement), morning stiffness >30 minutes, alternating buttock pain (sacroiliitis), and over years can fuse the spine. Onset is typically in young adults (15–35 years). Early diagnosis matters because biologics (anti-TNF, IL-17 inhibitors) can dramatically reduce inflammation and slow structural damage if started early.
In Indian rheumatology practice, HLA-B27 is part of the workup for any young adult with chronic inflammatory back pain (>3 months duration), enthesitis (heel, Achilles, plantar fascia pain), recurrent uveitis, or asymmetric oligoarthritis of the lower limbs. The test is also informative in first-degree relatives of AS patients. Important context: HLA-B27 is a genetic marker, not a disease — about 5–8% of healthy Indians are HLA-B27 positive without ever developing disease, so the test must be interpreted with symptoms and imaging.
How to prepare
No fasting required. No special preparation. Continue all medications. The test is a one-time genetic typing — the result does not change over time.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| HLA-B27 (Positive / Negative)[1][2][3] | Negative (Indian general population: ~6–8% positive) | Negative HLA-B27 makes axial spondyloarthritis less likely but does not rule it out — about 10% of AS patients are HLA-B27 negative. | Positive HLA-B27 in someone with inflammatory back pain or characteristic features supports a diagnosis of spondyloarthritis. In an asymptomatic person, HLA-B27 positivity carries only a 2–10% lifetime risk of developing AS — not enough to act on alone. |
HLA-B27 prevalence in spondyloarthritis-related conditions
| Condition | HLA-B27 positivity |
|---|---|
| Ankylosing spondylitis | ~90% |
| Reactive arthritis | ~70% |
| Acute anterior uveitis | ~50% |
| Psoriatic arthritis (axial) | ~50% |
| IBD-related arthritis (axial) | ~50% |
| Healthy Indian population | ~6–8% |
Frequently asked questions
Does positive HLA-B27 mean I will get ankylosing spondylitis?
No. Most HLA-B27 positive people (about 90–95%) never develop AS. The result only matters if you also have symptoms — inflammatory back pain, recurrent uveitis, enthesitis. A rheumatologist will interpret the result in context.
Do I need to fast?
No fasting required.
Should my family members be tested?
Routine screening of asymptomatic relatives is not recommended because positivity alone has limited clinical implications. Relatives with back pain or eye inflammation should see a rheumatologist.
Can the result change over time?
No. HLA-B27 is a genetic test. The result is the same throughout life.
I am HLA-B27 negative but have AS — is that possible?
Yes. About 10% of AS patients are HLA-B27 negative. Imaging (MRI sacroiliac joints showing active sacroiliitis) plus clinical features make the diagnosis.
Will biologic treatment depend on HLA-B27 status?
No. Biologics (anti-TNF, IL-17) work in both HLA-B27 positive and negative spondyloarthritis. The test guides diagnosis, not treatment selection.
How long does the report take?
Typically 2–3 days.
Related Autoimmune / Rheumatology tests
Tests commonly ordered alongside HLA-B27, or that help interpret an unexpected result.
Sources & references
- NIH MedlinePlus — HLA-B27 Test · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Ankylosing Spondylitis · accessed 2026-05-30T00:00:00.000Z
- ACR — Spondyloarthritis Guideline · accessed 2026-05-30T00:00:00.000Z
- EULAR — Management of Axial Spondyloarthritis · accessed 2026-05-30T00:00:00.000Z
Book with Zelnoo
Get your HLA-B27 test done at home — transparent prices, NABL-accredited labs.
Zelnoo lets you compare diagnostic test prices across NABL-accredited labs in Mumbai & Thane, book a free home phlebotomist visit, and receive digital reports in 24–48 hours into a consent-first report vault. No subscriptions, no membership fees — pay only for the test you book.
Book HLA-B27 now