POS0647 A COMPARISON OF 20 YEAR DISABILITY OUTCOMES IN VALIDATED CASES OF RHEUMATOID ARTHRITIS AND PSORIATIC ARTHRITIS IN THE NORFOLK ARTHRITIS REGISTER

Abstract

BackgroundRheumatoid arthritis (RA) and psoriatic arthritis (PsA) are common inflammatory rheumatic diseases with distinct clinical phenotypes, that can both result in significant disability. Whilst some data in selected samples report no difference in Health Assessment Questionnaire scores (HAQ) between RA and PsA(1), there is a lack of definitive long term population based data.The Norfolk Arthritis Register (NOAR) is an inception cohort of early inflammatory arthritis established in 1989, with over 4,500 cases of new onset inflammatory arthritis. Cases were recruited in primary care or from hospital clinics, and inclusion criteria were age >16 years with 2 swollen joints lasting ≥4 weeks. Data was collated on demographics and disability through Health Assessment Questionnaires (HAQ) over variable years of follow up (0-20 years); HAQ scores values range from 0 to 3, and the higher the score the greater the disability [2].ObjectivesOur aim was to compare differences between both baseline and follow-up HAQ scores in RA and PsA, in cases selected from the same base population and followed continuously for over 20 years.MethodsCases included in this study were recruits into NOAR, who were followed at intervals of 1, 2, 3, 4, 5, 7, 8, 10, 12, 15, 18 and 20 years. Cases of RA were defined using American College of Rheumatology (ACR) criteria; cases of PsA were classified by retrospective clinical record review.Cases with RA were compared to cases with PsA, and data analysis was carried out in R. Independent samples t-tests were used to assess statistical significance of unadjusted HAQ scores.ResultsA total of 1,812 cases of RA (85.4%) and 308 cases of PsA (14.5%) were identified with complete data on sex and age within the NOAR cohort who had recorded HAQ scores. The mean age of onset for RA was 56.3 years (min 18.6 – max 88.6; SD 13.9), and 47.3 years for PsA (min 16 – max 79.9, SD 13.1).Baseline HAQMean baseline HAQ scores were higher for RA at 0.854 (SD 0.704) when compared with PsA at 0.706 (SD 0.688) (p<0.001).Females had higher baseline HAQ scores than males (0.915 vs 0.677) consistent across both disease types which was statistically significant (RA – 0.919 vs. 0.716, p <0.001: PsA – 0.885 vs. 0.533, p <0.001).Follow-up HAQCases were followed up to 20 years. 1,812 cases of RA were identified at baseline, decreasing to 1552 with 1-year follow up (85.6%) and 165 cases with 20-year follow up (9.1%). 308 PsA cases were identified at baseline, 248 followed up at 1-year (80.5%) and 21 cases for 20-years (6.8%).Figure 1 illustrates that cases with RA had higher mean HAQ scores than PsA throughout a follow up period of up to 20 years. Mean HAQ scores accumulated over the follow up period for RA, whilst there was a decrease in HAQ scores after 12 years of follow up for those with PsA before increasing after 18 years.Figure 1.A comparison of the mean Health Assessment Questionnaire scores between Rheumatoid Arthritis and Psoriatic arthritisConclusionThe NOAR cohort is unique in its long follow up period of up to 20 years, allowing for the assessment of HAQ longitudinally. The relationship between higher HAQ scores in RA than PsA holds for both baseline HAQ scores and follow-up HAQ scores throughout the follow-up period, supporting the association of RA with greater disability. We hypothesise that this may be due to the nature of joint damage and other comorbidities associated with RA. We also demonstrate from this data that females present with statistically higher baseline HAQ scores than males within both diseases.In conclusion, there are evident trends with higher HAQ scores in RA over PsA consistent over time.