POS1041 PREVALENCE, INCIDENCE AND ANTIRHEUMATIC DRUG USE IN PSORIATIC ARTHRITIS (PsA) IN NORWAY
Authors: A. Kerola, J. Sexton, S. Rollefstad, G. Wibetoe, C. S. Crowson, E. Haavardsholm, T. K. Kvien, A. G. Semb
Journal: Annals of the Rheumatic Diseases (2021)

Background: Incidence estimates of PsA in Norway have varied from 6.9/100,000 person-years (pyrs) in Northern Norway to 41.3/100,000 pyrs in Central Norway, and point prevalence estimates have ranged from 1.3 to 6.9 per 1,000 adult inhabitants 1,2 , while nationwide epidemiologic data on PsA in Norway have been lacking. Objectives: To estimate prevalence, incidence and use of disease-modifying antirheumatic drugs (DMARDs) among PsA patients in Norway. Methods: The Norwegian Cardio-Rheuma register includes pseudonymized data from the total Norwegian population ≥18 years of age during 2008-2017, identified from the National Population register. Demographic and socioeconomic data were retrieved from Statistics Norway. Data on public or private somatic specialized care episodes were collected from the Norwegian Patient register (NPR) [ICD-10 codes for diagnoses and medical procedure codes for biologic DMARD infusions]. Information on dispensed DMARD prescriptions was captured from the Norwegian Prescription Database. Based on NPR data, PsA cases were defined as persons fulfilling three criteria: 1) 1st episode with ICD-10 code M07.0-M07.3 or L40.5 as main or contributory diagnosis (index date), 2) 2nd episode with code M07.0-M07.3 or L40.5 within 2-year period following index date, 3) an episode in internal medicine or rheumatology clinic with recorded M07.0-M07.3 or L40.5 within 2 years from index date. Years 2008-2010 served as a look-back period to identify prevalent PsA cases. To estimate pyrs at risk, we calculated number of individuals aged ≥ 18 years living in Norway on the 1 st of January of each year 2011-2015 multiplied by one year (prevalent PsA cases excluded). Age- and sex-standardized incidence rates were calculated with 5-year age groups using the Norwegian adult population on January 1 st 2015 as the standard. Results: During the look-back period 2008-2010, 7,697 cases fulfilled the PsA definition. In total, 6,183 incident PsA cases were identified during 2011-2015 (incidence 32/100,000 pyrs, 28 among men and 35 among women). Based on a sensitivity analysis comprising 5,065 PsA cases with no dispensed DMARD prescriptions ≥12 months before index date, incidence was slightly lower (26/100,000 pyrs). Patient characteristics and DMARD use are shown in Table 1. The incidence was highest among those aged 50-59 years in both sexes (Figure 1). PsA incidence was lower among those with higher education level (crude/age- and sex-standardized incidence per 100,000 pyrs for those below upper secondary education 34/38, upper secondary or post-secondary non-tertiary education 36/36, higher education 26/25). Point prevalence of PsA was 3.3/1,000 adult inhabitants on January 1 st 2016. Table 1. Characteristics and treatment penetration of incident PsA patients 2011-2015 All Excluding cases with DMARDs &gt;1 yr prior to index date N 6183 5065 Women, n (% ) 3442 (55.7) 2783 (54.9) Age at index date, median (IQR ) 50.5 (40.7 - 59.8) 49.9 (40.2 - 59.3) Use of DMARDs after index date, n (% ) 12 months 24 months 12 months 24 months Any conventional DMARD 3706 (59.9) 4048 (65.4) 2894 (57.1) 3184 (62.9) Methotrexate 3313 (53.6) 3650 (59.0) 2638 (52.1) 2933 (57.9) Sulfasalazine 440 (7.1) 586 (9.5) 330 (6.5) 457 (9.0) Any biologic DMARD 842 (13.6) 1197 (19.4) 485 (9.6) 771 (15.2) TNF-inhibitors 810 (13.1) 1154 (18.7) 477 (9.4) 758 (15.0) Oral glucocorticoids 1773 (28.7) 2240 (36.2) 1449 (28.6) 1807 (35.7) Any DMARD or glucocorticoids 4365 (70.6) 4742 (76.7) 3384 (66.8) 3725 (73.5) Conclusion: Our estimate of PsA incidence and prevalence are in the mid-range compared to studies from smaller regions in Norway. Methotrexate was initiated for more than half of PsA cases within one year from index date, whereas 19% had used biologic DMARDs within two years. References: [1]Hoff M, Gulati A, Romundstad P et al. Prevalence and incidence rates of psoriatic arthritis in central Norway: data from the Nord-Trondelag health study. Ann Rheum Dis 2015;74:60-64. [2]Nossent J &amp; Gran J. Epidemiological and clinical characteristics of psoriatic arthritis in northern Norway. Scand J Rheumatol 2009; 8:251-5. Acknowledgements: This work has been supported by a research grant from FOREUM Foundation for Research in Rheumatology. Disclosure of Interests: Anne Kerola Speakers bureau: Boehringer-Ingelheim, Consultant of: Pfizer, Gilead and Boehringer-Ingelheim, Joseph Sexton: None declared, Silvia Rollefstad: None declared, Grunde Wibetoe: None declared, Cynthia S. Crowson: None declared, Espen Haavardsholm: None declared, Tore K. Kvien Speakers bureau: Amgen, Celltrion, Egis, Evapharma, Ewopharma, Hikma, Oktal, Sandoz, Sanofi, Consultant of: AbbVie, Amgen, Biogen, Celltrion, Eli Lilly, Gilead, Mylan, Novartis, Pfizer, Sandoz, Sanofi, Grant/research support from: research funding to Diakonhjemmet Hospital from AbbVie, Amgen, BMS, MSD, Pfizer and UCB, Anne Grete Semb Speakers bureau: AbbVie, Bayer, Lilly, Novartis, Sanofi, Consultant of: Sanofi, Grant/research support from: Collaborative research support from Lilly, outside the submitted work.