Background/Purpose: There is little data on the 20 year outcome of patients with inflammatory polyarthritis (IP). Hence the aim of this study was to describe patients with IP over long term follow up, including disease activity, disability and surgery.

Methods: Adults, aged ≥16 with ≥2 swollen joints for ≥4 weeks, recruited from 1990-1994 to the Norfolk Arthritis Register (NOAR) were included in this study. Baseline assessments included demographics, 51 swollen / tender joint counts and HAQ. RF, ACPA and CRP were measured from stored blood samples taken every 5 years; DAS28-CRP scores were calculated.  Patients were re-assessed at years 1-3, 5, 7, 10, 15 and 20 years and self-report major orthopaedic surgeries data were also collected at these visits. Differences in the progression of disability over time based on gender and other baseline characteristics were assessed using a random effects model. The association between demographics, disability and disease activity and risk of first surgery was assessed using the Cox proportional hazard model. Censoring occurred when patients left the cohort. Mortality rates were calculated, using 15^th December 2014 as censor date.

Results: Of 1022 patients (60.1% met the 2010 ACR RA criteria) included at baseline, 354 (34.6%) completed 20 years follow-up. 404 (39.5%) died during follow up (mortality rate: 22.6 / 1000 patient years). At baseline, median (IQR) swollen / tender joint counts were 6 (2-13) / 7 (3-16), and HAQ was 0.8 (0.3-1.4). After baseline, median joint counts improved and remained low (see table). The median HAQ (IQR) score dropped to 0.5 (0.0 -1.3) after 1 year before increasing to 0.9 (0.3-1.6) at 10 years and 1.0 (0.3-1.8) at 20 years. Median DAS28-CRP showed a similar trend. In total, 237 (23.2%) patients underwent at least 1 major joint surgery. The probabilities of patients completing 10 / 20 years of follow-up without surgery were 0.84 and 0.70 respectively. Higher age at onset (HR 1.01; 95% CI 1.00-1.02 per year), baseline HAQ (HR 1.35; 95% CI 1.03 -1.78) and baseline CRP level (HR 1.01; 95% CI 1.00-1.01 per mg/l) were associated with an increased risk of first surgery. The median (IQR) number of surgeries per patient was 2 (1-3). Men were older than women at baseline (mean 55.7 vs 55.2 years, p = 0.0012) whilst women had worse median HAQ scores (0.9 vs 0.5, p<0.0001) and more swollen (7 vs 4, p<0.0001) and tender joints (8 vs 6, p=0.0016).Women had higher HAQ scores than men over 20 year follow up (β coef. 0.007; p<0.001) using a random effects model.

Conclusion: Over 20 years patients’ disease activity was well controlled. Median disability rose progressively but slowly after 5 years. Higher baseline HAQ and disease activity scores were associated with joint surgery during follow-up.