Anti-Cyclic Citrullinated Polypeptide Antibodies are used clinically to diagnose rheumatoid arthritis with high specificity and sensitivity. Anti-Cyclic Citrullinated Polypeptide Antibodies are cyclic polypeptide fragments, predominantly IgG type antibodies. Anti-cyclic citrullinated polypeptide antibodies are spontaneously secreted by B-lymphocytes of patients with rheumatoid arthritis, whereas B-lymphocytes of patients with other diseases and the normal population do not spontaneously secrete anti-cyclic citrullinated polypeptide antibodies. Therefore, the sensitivity and specificity of anti-cyclic citrullinated polypeptide antibodies for the diagnosis of rheumatoid arthritis is relatively high, and the higher the value, the higher the relative diagnostic sensitivity. The higher the value, the higher the relative diagnostic sensitivity. An increase in this value at an early stage suggests a greater likelihood of joint damage. Positive anti-cyclic citrullinated polypeptide antibodies require further examination to rule out the presence of autoimmune diseases, and need to be combined with antinuclear antibodies, C-reactive protein, blood sedimentation, rheumatoid factor to determine the presence of rheumatoid arthritis, and need to be combined with the patient’s clinical symptoms, joint ultrasonography or X-ray examination to confirm the diagnosis. If the level of anti-cyclic citrullinated polypeptide antibody is found to be elevated, consult the rheumatology and immunology department of a regular hospital for diagnosis and treatment.