RESUMO
Objective To evaluate the role of rheumatoid factor (RF), anti-cyclic citrullinated peptide antibody (ACCP) and anti-keratin antibody (AKA) in patients with rheumatoid arthritis (RA).Methods Serum levels of RF, ACCP and AKA were examined in 82 RA and 56 non-RA patients and their sensitivity and specificity for the diagnosis of RA were exmined. Statistical analysis was performed to test the association between ACCP/AKA and number of tender joints and swollen joints, ESR, CRP, disease activity score (DAS) or Ritchie's articular index (RAI). Results ROC curve was performed for each single auto-antibody and various combinations of any two of the above antibodies. The area under the ROC curve was over 0.5 (P<0.05). The specificity of ACCP and AKA was 91.1% and 92.9% respectively. RF, ACCP and AKA were all sensitive markers for the diagnosis of RA and the sensitivity could be as high as 95.1% when one of these markers was positive. There were statistical differences in the number of swollen joints, ESR and DAS between ACCP positive group and ACCP negative group (P<0.05) and statistical significant difference was observed in tender joint count, swollen joint count, ESR and DAS between AKA positive and negative groups (P<0.05). Conclusion Combined test of ACCP, RF and AKA is useful in routine RA diagnosis.ACCP and AKA may be clinical markers for predicting disease activity and prognosis.