Background Previous research has suggested that the severity of rheumatoid arthritis (RA) has decreased over time.
Objectives To examine the pattern of disease severity in patients with inflammatory polyarthritis (IP) at time of registration into the Norfolk Arthritis Register (NOAR).
Methods NOAR is a primary-care-based cohort of adults with recent onset IP (≥2 swollen joints lasting for >4 weeks). Disease related information collected at baseline includes 51- swollen and tender joint counts, HAQ, and DAS28. Blood is collected and C - reactive protein (CRP), Rheumatoid Factor (RF), and Anti-Citrullinated Peptide Antibodies (ACPA) are measured. In this study, patients with a symptom duration of <2 years at baseline were grouped into four cohorts depending on the NOAR recruitment phase: (1) 1990-1994; (2) 1995-1999; (3) 2000-2004; (4) 2005-2008. Three sub-samples were also evaluated: i) referred first to NOAR by their general practitioner; ii) DMARD naive at baseline; iii) met the ACR/EULAR 2010 RA criteria at baseline. Linear or median regression analyses were conducted to examine baseline HAQ or DAS28 scores over time. A quadratic term for calendar year of assessment by NOAR was included as a predictor and if significant, cohort was included to examine if the rate of change in scores over time differed between cohorts. Confounders included gender, RF and ACPA positivity, and age at symptom onset.
Results In total 3045 patients were evaluated: Cohort 1=1022; Cohort 2=883; Cohort 3=631; Cohort 4=509 (Table). Calendar year of assessment was a significant predictor of lower DAS28 scores over time for the total sample (adjß= -0.0007, 95% CI -0.001, -0.0001), and each sub-sample, indicating improved disease activity over time. Within the total sample, and the DMARD naive sub-sample, there was a significant effect of ‘Cohort’, and a significant ‘Calendar year by Cohort’ interaction indicating the rate of change in DAS28 scores over time differed between cohorts. Calendar year of assessment was not a significant predictor of HAQ scores for the total sample (adjß=0.0002, 95% CI -0.0002, 0.001), and was also a significant predictor of increased HAQ scores for the sub-sample who met the ACR/EULAR 2010 RA criteria, indicating no improvement in functional disability over time.
Conclusions Baseline disease activity has decreased over time and may not be solely attributable to the increased use of DMARDs. However, there has been no improvement in levels of functional disability.
Acknowledgements Funded by Arthritis UK and GlaxoSmithKline
Disclosure of Interest None Declared
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