HLA B27 (human leukocyte antigen) is a gene in our body . It is a normal genetic variant. HLA B27 can be positive in upto 8% of the normal population. A positive HLA B27 test does not mean a patient has 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 positivity is associated with a variety of diseases like ankylosing spondylitis, psoriasis, inflammatory bowel disease, reactive arthritis etc. If HLA B27 test is positive usually there is no need to have this test again. It does not change 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…
