HLA-B27 is a structure on the surface of human leukocytes, which plays a very important role in the recognition of bacteria and viruses by the immune system, and is a structure that is necessary for human survival in nature. A certain combination may predispose to diabetes, another to hypertension, and a B27 structure may predispose people to ankylosing spondylitis, with roughly one in every 300-400 people in the general population. In B27-positive people, the probability of ankylosing spondylitis is about one in 20, which is much higher and provides a diagnostic reference for doctors. However, it is important to understand that 95% of these positive individuals will not develop ankylosing spondylitis. Relying on this indicator to make a diagnosis can lead to misdiagnosis in a large percentage of patients. At least 10% of people with ankylosing spondylitis will be negative for B27. The B27 alone may lead to underdiagnosis in this group of patients. HLA-B27 is actually a genetically determined protein structure on the surface of a cell, which is different for each person, and is an important aspect that really determines the uniqueness of a person, such as paternity testing and crime scene identification, which detects these cell surfaces. So no matter how disguised a criminal is, his true identity can be identified through the testing of these things. So whether a person is positive or negative for HLA-B27 is determined by the parents and does not change throughout life. B27 positive means negative for other genes, which may increase the chance of developing ankylosis but decrease the chance of developing other diseases. There is no such thing as perfection, but it is the imperfection that makes the world so rich and colorful. Being positive and negative for HLA-B27 is something your parents gave you and will never change, and it is an important trait for you. It does not mean that you are sick and certainly cannot be diagnosed by this, whether positive or negative is normal.