The normal value of anti-cyclic citrullinated peptide antibody varies according to the clinical test method, usually less than 5RU/ml. Anti-cyclic citrullinated peptide antibody is an autoantibody with synthetic cyclic citrullinated peptide as antigen, which has high sensitivity and specificity for rheumatoid arthritis, and anti-cyclic citrullinated peptide antibody is one of the indicators for the diagnosis of rheumatoid arthritis. It is often detected by enzyme-linked immunosorbent assay (ELISA), etc. The normal reference range is usually attached to the test report, which varies from hospital to hospital and from test to test. Usually less than 5RU/ml. When the anti-cyclic citrullinated peptide antibody is greater than the normal reference value, the diagnosis of rheumatoid arthritis cannot be made solely on the basis of the positive anti-cyclic citrullinated peptide antibody, and further examination is needed to clarify the cause of the disease. Through the examination of rheumatoid factor, blood sedimentation, C-reactive protein, anti-keratin antibody, anti-perinuclear factor and MCV antibody, etc., the doctor can make a diagnosis of the disease based on the examination results and the clinical manifestations of the patient. Patients should not judge or diagnose on their own based on the results of a single test. It is recommended that they consult a doctor in a timely manner, who will analyze and diagnose the disease according to the specific situation.