HLA B27 (human leukocyte antigen) is not a disease. It is a gene in your body.
A positive HLA B27 test does not mean you have a disease. If you look at the whole population the majority of people carrying this gene will not develop ankylosing spondylitis. The usefulness of the test depends on the context that it is ordered in. History and examination is really useful.
HLA-B27 is a normal genetic variant. HLA B27 can be positive in upto 8% of normal population.
HLA B27 positivity is associated with a variety of diseases like ankylosing spondylitis, psoriasis, inflammatory bowel disease, reactive arthritis etc.
If your HLA B27 test is positive usually there is no need to have this test again. It does not disappear even after treatment.
Around 80 to 90% of patients with ankylosing spondylitis tests positive for HLA-B27.
If you look indiscriminately at the whole population, only 10-15% of those with this HLA-B27 gene will end up developing ankylosing spondylitis or another type of spondyloarthritis.
History suggestive of inflammatory back pain should prompt a doctor to order the HLA-B27 test. In this context, a positive HLA B27 test is useful in making the diagnosis.
Please note a negative HLA-B27 test does not completely rule out the diagnosis of ankylosisng spondylitis. Around 10-20% of patients with proven ankylosing spondylitis will test negative for HLA B27.
Treatment depends on the final diagnosis and severity of the disease.
Symptoms of Inflammatory Back Pain –
1. Starts before the age of 40 years
2. Comes on slowly over time
3. Worse in the mornings and evening
4. Stiffness in the mornings or after period of inactivity