Human antigen leukocytes or HLAs are proteins present in the surface of white blood cells. HLAs usually play an important role in protecting the body from harm. However HLA-B27, a certain type of protein, may be related to immune system dysfunction. The presence of HLA-B27 could imply that the immune system is attacking healthy cells and tissue by mistaking them for harmful agents. This condition is called autoimmune disease.
Testing for HLA-B27 helps to detect if this protein is present or absent. Doctors usually order the test based on the symptoms of an individual.
The presence of HLA-B27 is indicative of various autoimmune diseases such as ankylosing spondylitis which is a severe form of arthritis, reactive arthritis and anterior uveitis. An HLA B27 test may be ordered to monitor the progression of diseases such as these.
The test may also be used when an individual manifests specific symptoms such as joint pain and inflammation, swelling of the neck, chest or spine and frequent infection of the eye. In such cases, the HLA-B27 test may be used along with other blood tests.
In some cases, the HLA-B27 test may be administered on individuals undergoing a bone marrow or kidney transplant. HLA antigen tests in these cases help to match donor tissue with organ recipients.
The HLA-B27 test involves obtaining a sample of blood usually from the arm. There may be a mild prick when the needle is inserted, followed by a slight throbbing sensation. The blood is sent to a laboratory for analysis. No special preparation is required before the test. However it is advisable to ask your doctor if you need to stop the intake of any medication before the test.
Normal or negative test results indicate the HLA-B27 antigen is absent. A positive result indicates a risk for certain autoimmune conditions. Such disorders occur when the immune system attacks healthy body tissue mistaking it for harmful agents.
The HLA-B27 protein is found normally in some Caucasians and this is not necessarily indicative of any disease.
Obtaining a blood sample usually involves minimal risk. There may be slight discomfort or pain as the needle is inserted into the arm. Mild throbbing around the puncture site also commonly occurs after the test. However if more serious symptoms such as light-headedness, fainting, excessive bleeding or hematoma occur, special medical attention may be necessary.