P01 Incidence of juvenile idiopathic arthritis in the United Kingdom: estimates from a national primary care dataset

Abstract

Poster presentation Tuesday 8 October Background Juvenile idiopathic arthritis (JIA) is the most common childhood onset inflammatory arthritis. The last estimates of incidence of JIA in the UK are from nearly 30 years ago, prior to international classification consensus and the emergence of paediatric and adolescent rheumatology as a specialty. The aim of this study was to estimate incidence of JIA from primary care records in the UK since 2000. Methods The study used data from the Clinical Practice Research Datalink (CPRD), a database of UK primary care records broadly representative of the UK in terms of age, gender and ethnicity. A pre-defined list of JIA Read codes were used to identify incident cases annually from 2000-2018. Incidence rates (IR) with 95% confidence intervals(CI) were calculated and stratified by age and gender. The denominator was the population of CPRD <16 years old on the 31st December each year. Direct standardisation, applying Office for National Statistics population data, was used to estimate the UK IR. IRs in 5-year groupings were calculated 2000-2015 to identify change over time. Results Between 2000-2018, there were 1927 incident cases of JIA, from a total of 23,328,676 children <16 years old in CPRD. The total IR (95% CI) was 8.26 (7.90-8.64) per 100,000 population; for females and males respectively it was 9.83 (9.27-10.43) and 6.78 (6.33-7.27) per 100,000. Age-adjusted direct standardisation to the UK population estimated a total IR of 9.66 per 100,000 person-years. By age group, there appeared to be a lower incidence in middle childhood compared to early childhood and adolescents, as well as infancy where lower rates may be due to difficulties recognising the disease (Table 1). IRs over time did not appear to change. P01 Table 1: Incidence rates by age group Age (years) Denominator Cases IR (95% CI) Per 100,000 0-2 1739417 113 6.5 (5.40-7.81) >2-6 5763003 534 9.27 (8.51 – 10.08) >6-12 9464988 693 7.32 (6.80-7.90) >12-15 6361268 587 9.22 (8.51-10.01) Conclusion This is the first study to provide contemporary UK estimates of the incidence of JIA for nearly 30 years. JIA was more common in females compared to males, and in early childhood and adolescence compared to other age groups. Incidence appeared to be stable over fifteen years. These data provide important information for patients, their families and healthcare providers; in addition, they are vital for appropriate resource planning and service provision in paediatric and adolescent rheumatology. Conflicts of Interest The authors declare no conflicts of interest.