Objectives: To investigate the influence of early disease modifying anti-rheumatic drug (DMARD) treatment on long-term functional outcome in patients with recent onset inflammatory polyarthritis (IP), and the impact of the duration of first and subsequent DMARD treatment.
Methods: 642 subjects from a primary-care registry of patients with new onset IP, recruited 1990-1994, were followed for 10 years. Mean change in HAQ scores between baseline and 10 years were compared by time to and time on first DMARD treatment and total time on treatment, using linear regression. Adjustment for time dependent confounders and censoring was performed using marginal structural weights.
Results: When adjusted for baseline and subsequent disease severity, those treated early (<6 months from symptom onset) experienced a non-significant improvement in function compared to those never treated (adjusted mean difference in change (adj_MDIC) in HAQ -0.24; 95% CI -0.58, 0.09); and a significant benefit for each additional month of treatment within 6 months of the onset of symptoms (adj_MDIC -0.10 95% CI; -0.19, -0.02). Patients who discontinued their first DMARD within 6 months experienced a significant deterioration in long-term function (adj_MDIC in HAQ 0.28 95% CI; 0.04, 0.52), while those who continued their first therapy for greater than 3 years experienced an improvement (adj_MDIC in HAQ -0.37; 95% CI -0.77, 0.04).
Conclusions: We have demonstrated the importance of time to and response to first DMARD treatment and total duration of DMARD treatment in modifying the 10 year function in patients with IP.