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Very early therapy of rheumatoid arthritis (RA) with disease-modifying antirheumatic drugs is associated with lower levels of joint destruction and a higher chance of achieving remission.1,–,5 Having symptoms for >12 weeks at treatment initiation is a strong and independent risk factor for a persistent disease course.1 3,–,5 These observations have led to the concept of the 'window of opportunity'.2 This hypothesis presumes that underlying disease processes are not fully matured in the very early stage of arthritis, making modulation more successful. However, putative biological mechanisms remain unexplored.
Anti-citrullinated protein antibodies (ACPA) precede arthritis development and are associated with a severe disease course.6 We hypothesised that the ACPA response broadens within the very early phase of RA and in doing so limits the 'window of opportunity'. Therefore, it was examined whether patients who were assessed within 12 weeks of symptom onset had a less broadened ACPA response than patients with longer symptom duration.
Three hundred and nine ACPA-positive patients (defined by anti-CCP2 positivity) fulfilling the 1987 ACR criteria for …