POS1442 THE PREVALENCE OF RHEUMATOID ARTHRITIS IN WESTERN AUSTRALIA EXTRAPOLATED FROM HOSPITALISATION AND BIOLOGICAL THERAPY USAGE DATA

Abstract

BackgroundRheumatoid arthritis (RA) is a heterogeneous chronic autoimmune disease that affects the synovial joint lining and may result in permanent joint destruction, premature death, and socio-economic burden.1 Although RA is one of Australia’s national health priority areas and gathering information about the RA burden of disease was one of the national action plans2, no published epidemiological study adequately describes RA prevalence and risk factors for frequent hospitalisations in Western Australia (WA) to date. An accurate prevalence estimate of this disease offers a framework for predicting present and growing healthcare service requirements in the future.3ObjectivesWe estimated RA period prevalence and identified risk factors of frequent RA hospitalisations, using linked administrative health and state-specific Australian Pharmaceutical Benefits Scheme (PBS) datasets in WA from 1995–2014.MethodsRA prevalence was calculated per 1000 hospital separations and biological therapy users. RA patients were identified in the WA linked health dataset using ICD codes 714.0–714.9 and M05.00–M06.99. Dispensing data on biological therapy for RA were obtained from PBS records and converted to defined daily doses/1000 population/day. Multivariate logistic regression was used to analyse risk factors for frequent RA hospitalisations (>2/year), controlling for sex, age, and geographic locations.ResultsA total of 17,125 RA patients were admitted to WA hospitals between 1995–2014. The total number of RA hospital separations was 50,353, averaging three hospitalisations per patient over 20 years. The RA period prevalence was 3.4 per 1,000 separations (0.34%), while the RA period prevalence based on biological therapy use was 0.36%. The corrected RA prevalence based on biological therapy usage was 0.36% and 0.72% for the 2005–2009 and 2010–2014 periods, respectively (Table 1). Female gender, age 60–69 years, and living in rural areas were all risk factors for frequent RA hospitalisations.Table 1.Total number of Rheumatoid Arthritis patients in Western Australia taking a standard dose daily (DDD) of RA biological therapy from 1995 to 2014.YearTotal RA bDMARDs utilisation (DDD/1000 population/day)WA general populationPrevalence of RA bDMARDs use in WA population (%)Number of RA patients use standard dose daily of bDMARDs at WA20030.011,952,7410.001420040.081,979,5420.0115820050.162,011,2070.0232920060.232,050,5810.0247620070.312,106,1390.0364320080.502,171,7000.051,09420090.602,240,2500.061,33820100.592,290,8450.061,36120110.632,353,4090.061,47520120.772,425,5070.081,85920130.662,486,9440.071,64920141.002,517,6080.102,510Abbreviations: bDMARDs, biologic disease-modifying anti-rheumatic drugs included Abatacept, Adalimumab, Certolizumab, Etanercept, Golimumab, Infliximab, Rituximab, Tocilizumab; DDD, defined daily doses; RA, Rheumatoid arthritis; WA, Western Australia.ConclusionBased on hospital and biological therapy data, the minimal prevalence of RA in Western Australia is 0.34–0.36%, which falls within the literature range. Older female RA patients in rural areas were more likely to be hospitalised, suggesting unmet needs in primary care access.