HLA-B27 is a blood test to look for a protein that is found on the surface of white blood cells. The protein is called human leukocyte antigen B27 (HLA-B27).
Human leukocyte antigens (HLAs) are proteins that help the body's immune system tell the difference between its own cells and foreign, harmful substances.
Human leukocyte antigen B27; Ankylosing spondylitis-HLA; Psoriatic arthritis-HLA; Reactive arthritis-HLA
How the Test is Performed
A blood sample is needed. Most of the time, blood is
How to Prepare for the Test
In most cases, no special steps are needed to prepare for the test.
How the Test will Feel
When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the Test is Performed
Your health care provider may order this test to help determine the cause of joint pain, stiffness, or swelling. The test may be done along with other tests, including:
- Erythrocyte sedimentation rate (
ESR) Rheumatoid factor
A normal (negative) result means HLA-B27 is absent.
What Abnormal Results Mean
A positive test means HLA-B27 is present. It suggests a greater-than-average risk for developing or having certain autoimmune disorders. An autoimmune disorder is a condition that occurs when the immune system mistakenly attacks and destroys healthy body tissue.
A positive result can help your provider make a diagnosis of a form of arthritis called spondyloarthritis. This kind of arthritis includes the following disorders:
- Arthritis related to
Crohn diseaseor ulcerative colitis
- Psoriatic arthritis (arthritis associated with psoriasis)
- Sacroiliitis (inflammation of the sacroiliac joint)
If you have symptoms or signs of spondyloarthritis, a positive HLA-B27 test may help confirm the diagnosis. However, HLA-B27 is found in some normal people and does not always mean you have a disease.
Risks from having blood drawn are slight, but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Chernecky CC, Berger BJ. Human Leukocyte Antigen (HLA) B-27 - blood. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:654-655.
Fagoaga OR. Human leukocyte antigen: the major histocompatibility complex of man. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 49.
Inman RD. The spondyloarthropathies. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 265.
McPherson RA, Massey HD. Overview of the immune system and immunologic disorders. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 43.
Review Date: 24/04/2017
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