Background Joint inflammation in Rheumatoid Arthritis is strongly associated with the development of joint damage. However, this association is highly different between patients, which may be explained by the presence of anti-CCP. Therefore it can be hypothesized that anti-CCP modifies the effect of joint inflammation on progression of joint damage.
Objectives To analyze whether the association between joint damage progression and Swollen Joint Count (SJC44), Erythrocyte Sedimentation Rate (ESR) or Disease Activity Score (DAS) is different for anti-CCP positive versus negative RA patients in the first three years of the disease.
Methods Follow-up data were used of the first three years from a subset of patients from the Nijmegen Inception Cohort with rated X-rays. Joint damage progression was assessed 1) as the absolute difference in Ratingen score and 2) dichotomized as erosive progression in at least one previously unaffected joint. Time averaged SJC44, ESR and DAS over three years were calculated. Anti-CCP titer ≥25 u/l was regarded as positive. Linear and logistic regression were used for analyses.
Results Data of 264 RA-patients were used, 180 (68%) were anti-CCP positive. In linear regression, anti-CCP was an effect modifier for the relationship between SJC44 and absolute joint damage progression (p=0.031). Stratification by anti-CCP resulted in beta’s of 0.46 and 1.12 for respectively anti-CCP negative and anti-CCP positive patients (see figure left). With up to five swollen joints, the probability of erosive progression in a previously unaffected joint was <20% in anti-CCP negative patients and >70% in anti-CCP positive patients (see figure right). The relationship between DAS and joint damage progression was modified by anti-CCP concerning the chance on progression in at least one new joint. The relationship between ESR and joint damage was not influenced by anti-CCP.
Conclusions The relationship between SJC44 and joint damage progression is different for anti-CCP positive and anti-CCP negative RA-patients (effect modification). For clinical practice, this means that the treatment target regarding swollen joint count should be lower for anti-CCP positive patients than for anti-CCP negative patients to prevent joint damage progression.
Disclosure of Interest None Declared