Anti-cyclic citrullinated peptide antibodies indicate a high probability of rheumatoid arthritis. Anti-cyclic citrullinated peptide antibodies are antibodies with a high specificity for rheumatoid arthritis, and a positive antibody indicates a 95% or higher probability of rheumatoid arthritis. However, not all patients with rheumatoid arthritis are positive, which means that some patients are negative for this antibody and this antibody is negative. The diagnosis of rheumatoid arthritis is not only based on this index, but also on rheumatoid factor, blood sedimentation, C-reactive protein and several other indicators. Ultrasound of joints also has a high value in the diagnosis of rheumatoid arthritis, and must be combined with clinical symptoms of multiple joint swelling and pain in order to make an accurate final diagnosis.