A positive HLA-B27 result is only one of the reference indicators for the diagnosis of ankylosing spondylitis. The HLA-B27 positive rate in patients with ankylosing spondylitis is as high as 90% to 96%, while the HLA-B27 positive rate in the general population is only 4% to 9%; the incidence of ankylosing spondylitis in HLA-B27 positive patients is about 10% to 20%, while the incidence in the general population is 1‰ to 2‰, a difference of about 100 times. All of this suggests that HLA-B27 is an important factor in the development of ankylosing spondylitis. However, it should be noted that, on the one hand, not all HLA-B27-positive individuals develop spondyloarthropathy, and on the other hand, about 5% to 20% of patients with spondyloarthropathy test negative for HLA-B27, suggesting that, in addition to genetic factors, other factors influence the development of AS, so HLA-B27 is an important genetic factor in the expression of AS, but not the only factor affecting the disease. Ankylosing spondylitis does not occur in 80% of HLA-B27-positive individuals, while 10% of patients with ankylosing spondylitis are HLA-B27-negative. Therefore, HLA-B27 positive does not necessarily mean that ankylosing spondylitis occurs, and HLA-B27 negative does not necessarily mean that ankylosing spondylitis does not occur, let alone that HLA-B27 positive is ankylosing spondylitis.