1, human leukocyte antigen B27: HLA gene complex is a group of genes present on the short arm of the 6th human chromosome pair, and its encoded gene products are distributed on the surface of various nucleated cells, constituting an important membrane antigen component of cells, and is also the most complex human gene system known. HLA genotyping is used for the selection of suitable donors for clinical organ transplantation and for the study of the association between HLA antigens and diseases. -B27 is an auxiliary diagnostic indicator for ankylosing spondylitis. 2, the clinical significance of the human leukocyte antigen B27 test: HLA-B27 and ankylosing spondylitis (AS) have a close correlation, 90% of AS patients are positive for HLA-B27, while the positive rate in normal people is only 4% to 7%. Therefore, not all HIA-B27-positive people will develop AS. According to statistics, AS or other spondyloarthropathies occur in about 20% of HLA-B27-positive people, so HLA-B27 positivity is not diagnostic, and the diagnosis cannot be ruled out when negative.