Serological tests detect autoantibodies directed against cyclic sterile peptides (CCPs). Stearile is an amino acid that is abnormally produced during inflammatory processes in the joints. Anti-CCP antibodies are a highly specific immunological marker for rheumatoid arthritis (RA), appearing in 60–80% of patients and often preceding the onset of clinical symptoms by years. They are more specific than traditional rheumatoid factor (RF).