RT Journal Article SR Electronic T1 Rheumatoid factor, but not anti-cyclic citrullinated peptide antibodies, is modulated by infliximab treatment in rheumatoid arthritis JF Annals of the Rheumatic Diseases JO Ann Rheum Dis FD BMJ Publishing Group Ltd and European League Against Rheumatism SP 299 OP 302 DO 10.1136/ard.2004.023523 VO 64 IS 2 A1 L De Rycke A1 X Verhelst A1 E Kruithof A1 F Van den Bosch A1 I E A Hoffman A1 E M Veys A1 F De Keyser YR 2005 UL http://ard.bmj.com/content/64/2/299.abstract AB Objectives: To analyse the effect of infliximab on IgM rheumatoid factor (RF) and anti-cyclic citrullinated peptide (CCP) antibodies, and determine whether baseline autoantibody titres (IgM RF and anti-CCP antibodies) are associated with changes in acute phase reactants. Patients and methods: 62 patients with refractory RA were treated with infliximab combined with methotrexate. At baseline and week 30, serum samples were tested for IgM RF by two agglutination assays, and for anti-CCP antibodies by an ELISA. Percentage change in C reactive protein (CRP) and erythrocyte sedimentation rate (ESR) was calculated. Results: At baseline and week 30 RF titres were reduced significantly during infliximab treatment (p<0.001 and pā€Š=ā€Š0.038, respectively), whereas anti-CCP antibodies were unchanged (pā€Š=ā€Š0.240). Baseline IgM RF titres, but not anti-CCP antibodies, correlated inversely with changes in CRP and ESR during treatment. Patients with a marked decrease in acute phase reactants had lower IgM RF titres than those with a smaller decrease in CRP and ESR; no significant differences were found for anti-CCP antibodies. Conclusion: The differential effect of infliximab treatment on IgM RF and anti-CCP antibodies, and the different predictive value on changes in acute phase reactants during infliximab treatment support the existing evidence that RF and anti-CCP antibodies are independent autoantibody systems in RA.