Evaluating relationships between symptom duration and persistence of rheumatoid arthritis: does a window of opportunity exist? Results on the Leiden early arthritis clinic and ESPOIR cohorts.

Background: A prolonged symptom or disease duration at treatment initiation is associated with unfavourable outcomes in rheumatoid arthritis (RA). It is unknown whether this relation is linear, referring to a common 'the-earlier-the-better principle', or whether a transient time frame in which the disease is more susceptible to treatment exists, referring to a 'window of opportunity'. To elucidate this, we evaluated the shape of the associations of symptom duration with persistence of RA.

Methods: Patients with 1987 RA treated with disease modifying antirheumatic drugs (DMARDs) in the Leiden Early Arthritis Clinic (EAC, n=738) and Evaluation et Suivi de POlyarthrites Indifférenciées Récentes (ESPOIR) (n=533) were studied. Cox proportional hazards regression models using natural cubic splines were performed; the log-HR on DMARD-free sustained remission (the opposite of RA persistence) during 5-year follow-up was plotted against symptom duration. Discrimination was measured using time-dependent receiver operator characteristic curves. Subanalyses were performed stratified for the DMARDs used (methotrexate or other conventional DMARDs) and for anticitrullinated peptide antibody (ACPA).

Results: 11.5% (85/738) and 5.4% (29/533) of EAC and ESPOIR RA patients achieved DMARD-free sustained remission. In both cohorts and all analyses, the curves depicting the log-HRs on remission in relation to symptom duration were not linear. The symptom duration with optimal discriminative ability was 14.9 weeks (95% CI 12.3 to 16.0; area under the curve (AUC) 0.61) in the EAC and 19.1 weeks (95% CI 12.3 to 28.0; AUC 0.59) in ESPOIR. For ACPA-positive RA, this was 11.4 weeks (95% CI 7.7 to 79.0; AUC 0.56) and for ACPA-negative RA 15.0 weeks (95% CI 9.7 to 48.7; AUC 0.56).

Conclusions: The association between symptom duration and RA persistence is not linear, suggesting the presence of a confined period in which RA is more susceptible to treatment.