A HLA-B27 positive test means that the patients tested is at increased risk of developing certain autoimmune diseases. If the person has symptoms such as chronic pain, inflammation, and/ or degenerative changes to bones ( on X-ray), then it supports a diagnosis of Ankylosing Spondylitis, Reactive Arthritis, or another autoimmune disorder that is related to HLA-B27+. This is especially true if the person is young, male, and if he experienced his first symptoms before the age of 40.

An HLA disease association is defined as a statistically increased frequency of the HLA haplotype in individuals with the disease compared to the frequency in individuals without the disease. This is expressed as a relative risk. For example, HLA-B27 appears in 80-90% of patients with ankylosing spondylitis. Expressed as a relative risk, an HLA-B27 positive individual is approximately 87 times more susceptible to developing ankylosing spondylitis compared to the general population.

HLA-B27 is Associated With Autoimmune Diseases

The prevalence of HLA-B27 varies between ethnic groups and populations worldwide but is generally not a very common haplotype. Only 8 percent of Caucasians, 4 percent of North Africans, 2 to 9 percent of Chinese, and 0.1 to 0.5 percent of Japanese people possess HLA-B27 positive blood test.

Ankylosing Spondylitis (AS) is the most common disease which affect about 85+% of HLAB27 positive persons it is an inflammatory disease in which some of the vertebrae of the spine fuse together, inhibiting mobility. An estimated 88 percent of people with AS are HLA-B27 positive, yet only a fraction of HLA-B27-positive people will develop AS. Other autoimmune diseases that are associated with an HLA-B27 haplotype include Crohn’s disease, ulcerative colitis, psoriasis, reactive arthritis, and uveitis.