Pos0998-hpr the epidemiology of primary sjogren’s syndrome: is it a rare disease?

Background Sjogren’s syndrome (SSj) is a systemic disease with autoimmune pathogenesis, with prevalent involvement of the lacrimal and salivary exocrine glands, classified as primary or secondary on the basis of the association with other rheumatic diseases. The epidemiological data in the literature are variable due to the heterogeneity of the populations examined and the different classification criteria used. In a recent systematic review by Baodon Qin et al. In a recent systematic review by Baodon Qin et al. the average incidence rate was 7 cases every 100,000 people/year (range 5-9) with higher values in the Caucasian and Asian populations, with a women/men ratio of 9.3 (95% CI 3.35 to 13.18), while the prevalence rate was 61 cases per 100,000 inhabitants (range 10-90) with a female/male ratio of 10.7 (95% CI 7.35-15.62). Objectives The aim of the study was to estimate the prevalence rate of primary SSj in real-life, through analysis of administrative data. Methods An epidemiological research was carried out as at 31 December 2020, through the analysis of all adult patients residing in Piedmont (northwest of Italy) with exemption code (EC) for SSj (code 030) and any association with other ECs for rheumatological pathologies or for pathologies considered according to the 2016 EULAR/ACR classification criteria; specifically, the EC were considered for rheumatoid arthritis, ulcerative colitis and Crohn’s disease, chronic hepatitis (active), HIV infection, affected subjects from malignant neoplastic pathologies, tumors of uncertain behavior, systemic lupus erythematosus, Hashimoto’s thyroiditis, undifferentiated connective tissue disease; mixed cryoglobulinemia, antiphospholipid antibody syndrome (primary form), primary and familial amyloidosis, hereditary/familial autoinflammatory syndromes, microscopic polyangiitis, polyarteritis nodosa, sarcoidosis, dermatomyositis, polymyositis, mixed connective tissue disease, progressive systemic sclerosis. Results There were 3889 patients with EC for SSj as at 31 December 2020, of which 2611 with active EC. The number of assisted people alive with the aforementioned exemption was 2601, while those with other exemptions in the list were 1020. Of these patients, 1581 had only the exemption from code 030 as at 31 December 2020; the distribution of the other pathologies analyzed is shown in the tables below (Table 1). Of the total number of patients with active exemption, 2442 were female, while 159 were male, with a female/male ratio of 15.3; the distribution by gender is shown in Figure 1. Considering that the Piedmont population on 31 December 2020 was 4 274 945 inhabitants (ref: National Institute of Statistics), the estimated prevalence rate was 4.7 cases per 10 000 inhabitants. Table 1. Distribution of EC in patients residing in Piedmont as at 31/12/2020 Diseases with EC N of patients Rheumatoid Arthritis 250 Ulcerative colitis and Crohn’s disease 18 chronic hepatitis 52 HIV infection 2 Systemic Lupus Erythematosus 122 Subjects affected by malignant neoplastic pathologies 330 Hashimoto’s thyroiditis 280 Undifferentiated Connective Tissue Sisease 86 Mixed Cryoglobulinemia 6 Antiphospholipid Antibody Syndrome 8 Primary And Familial Amyloidosis 3 Hereditary/Familial Autoinflammatory Syndromes 1 Microscopic Polyangiitis 2 Polyarteritis Nodosa 1 Sarcoidosis 5 Dermatomyositis 2 Polymyositis 5 Mixed connective tissue disease 25 Progressive systemic sclerosis 56 Figure 1. Distribution by gender of patients residing in Piedmont with exemption for Sjogren’s Syndrome. F: Female; M: Male Conclusion This research has some limitations, including the retrospective design and the use of administrative data which may be affected by the aforementioned difficulty of classification as well as incorrect attributions of exemption, both for SSj and for associated pathologies. Our research highlights a number of patients with primary SSj lower than the prevalence figure that defines a rare disease, i.e. a prevalence of less than 5 cases per 10,000 inhabitants. Further studies are needed to confirm these preliminary data. Reference [1]Baodong Qin et al. Ann Rheum Dis. 2015 Nov;74(11):1983-9. Acknowledgements: NIL. Disclosure of Interests None Declared.