Ab0768 new insights on epidemiological data and impact of the covid-19 pandemic on iga vasculitis in children and adults in france: a nationwide cohort

Background IgA vasculitis (IgAV) is a rare autoimmune disease affecting small vessels. It is well established that the incidence is higher in children (3 to 26 per 100,000 children/year,) [1] than in adults (0.1 to 1.8 per 100,000 individuals/year) [1] . However others epidemiological data and impact of the COVID-19 on IgAV remain overlooked [2] . Objectives To collect and analyze epidemiological data on IgAV in both adults and children in France. Methods We conducted an observational study using a national database called “BNDMR” [3] (Banque Nationale de Données Maladies Rares) on IgA vasculitis (code ORPHA761), which gathered patients managed in the French rare disease expert network. The incidence was estimated from the date of diagnosis, and we calculated the median annual incidence over the period 2010-2022. We specifically assessed the north/south gradient (latitude of the residence higher/lower than the median of the latitudes), the seasonality, and the impact of the COVID-19 pandemic compared to other patients reported within the same period and addressed in the same expert centers used as controls. Results During this 12-year period, 1988 patients with IgAV were reported (1498 children; 490 adults). The male to female ratio was 1.57 for adults and 1.05 for children. The median IgAV annual incidence was 15 cases/year [IQR 9-30] and 82 cases/year [IQR 72-86] for adult and children cases respectively. Time to diagnosis was less than 1 month for both. Compared with other patients reported in the same expert centers, IgAV was more frequently reported in the southern part of France than in the north (OR 4.88 [95% confidence intervals: 4.17 - 5.74] in adults and OR 1.51 [1.35 - 1.68] in children). IgAV was also more frequently observed in winter than during the rest of the year in both adults (OR 1.60 [1.39 - 1.82]) and children (OR 1.22 [1.01 - 1.48]). The incidence of IgAV decreased during the COVID-19 pandemic period (from March 2020 to September 2022) in children (OR 0.62 [0.47 - 0.81]) but not in the adult population (OR 0.90 [0.76 - 1.06]). Conclusion Our study confirms the winter seasonality and sex ratio in IgAV [4,5] , but suggests that the incidence or the reporting of IgAV decreased in children during the COVID19 pandemia, possibly due to barrier measures [6] . The observed north/south gradient need confirmation. The main limitation of this study is a possible IgAV under-reporting as this study rely only on cases addressed in expert centers. References [1]Audemard-Verger A, Pillebout E, Guillevin L, Thervet E, Terrier B. IgA vasculitis (Henoch-Shönlein purpura) in adults: Diagnostic and therapeutic aspects. Autoimmun Rev . 2015;14(7):579-585. doi:10.1016/j.autrev.2015.02.003 [2]Deshayes S, Moulis G, Pillebout E, Aouba A, Audemard-Verger A. Positive predictive value of hospital discharge diagnosis code to identify immunoglobulin A vasculitis in France: A validation study. Eur J Intern Med . 2017;43:e18-e19. doi:10.1016/j.ejim.2017.05.025 [3]Jannot AS, Messiaen C, Khatim A, Pichon T, Sandrin A, BNDMR infrastructure team. The ongoing French BaMaRa-BNDMR cohort: implementation and deployment of a nationwide information system on rare disease. J Am Med Inform Assoc . 2022;29(3):553-558. doi:10.1093/jamia/ocab237 [4]Piram M, Maldini C, Biscardi S, et al. Incidence of IgA vasculitis in children estimated by four-source capture-recapture analysis: a population-based study. Rheumatology (Oxford ). 2017;56(8):1358-1366. doi:10.1093/rheumatology/kex158 [5]Gardner-Medwin JMM, Dolezalova P, Cummins C, Southwood TR. Incidence of Henoch-Schönlein purpura, Kawasaki disease, and rare vasculitides in children of different ethnic origins. Lancet . 2002;360(9341):1197-1202. doi:10.1016/S0140-6736(02)11279-7 [6]Kaya Akca U, Atalay E, Cuceoglu MK, et al. Impact of the COVID-19 pandemic on the frequency of the pediatric rheumatic diseases. Rheumatol Int . 2022;42(1):51-57. doi:10.1007/s00296-021-05027-7 Figure. Acknowledgements: NIL. Disclosure of Interests None Declared.