李军霞       　郭建瑞　     李小峰

 The serological examination of autoantibodies is a valuable diagnostic test for early rheumatoid arthritis ( RA ). The rheumatoid factor ( RF ) is an autoantibody directed to the Fc portion of the anti-denatured immunoglobulin G ( IgG ). As the first serological maker used in the diagnosis of RA, its sensitivity is 80% and specificity is 30%-40%. The anti-citrullinated protein/peptide antibody ( ACPA ) consists of different subfamily members, including anti-cyclic citrullinated peptide 1 ( anti-CCP1 ), anti-CCP2, anti-keratin antibody ( AKA ), anti-perinuclear factor ( APF ), anti-Sa-antibody, anti-peptidase A ( anti-pepA ), anti-pepB and anti-human citrullinated fibrinogen antibody ( AhFibA ). The sensitivity of ACPA for the early diagnosis of RA is about 50%-70%, while the specificity is over 95%. ACPA is associated with the RA disease activity. The cluster reaction is determined by different citrullinated epitopes in correspondence with different patients. The sensitivity of ACPA test is expected to increase when more than 2 citrullinated epitopes are detected. The specificity in the diagnosis of RA will be up to 99% when more than 2 autoantibodies are positive at the same time. Above all, the positive rate of early RA can be greatly increased with the combination of RF with ACPA.