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Objective.Genetic and environmental backgrounds influence the development of rheumatoid arthritis (RA). In Latin America, epidemiologic data are scarce. We aimed to determine the prevalence of RA in Chile in a population-based study.Methods.The National Health Survey was a cross-sectional household survey with a stratified multistage probability sample of 6233 participants performed between August 2016 and March 2017. A screening instrument for RA was applied to a random sample of 3847 subjects > 30 years old. Positive screening was defined by at least 1 of the following: 2 swollen joints for at least 4 consecutive weeks (past/present), and/or a diagnosis of arthritis in the past. Individuals with positive screening had rheumatoid factor, anticitrullinated protein antibodies, and C-reactive protein measured, as well as clinical examination performed by a rheumatologist. Self-report of doctor-diagnosed RA was also performed.Results.The screening questionnaire was applied to 2998 subjects. A positive screening was found for 783 (22.1%). Among subjects with positive screening, 493 (66%) had a clinical evaluation performed by a rheumatologist. Using the American College of Rheumatology/European League Against Rheumatism 2010 classification criteria, prevalence was 0.6% (95% CI 0.3–1.2). Prevalence was higher in women, and 3.3% of subjects self-reported having RA.Conclusion.According to this national population-based study, RA prevalence in Chile is 0.6% (0.3–1.2), a value similar to what has been found in developed countries and slightly lower than some Latin American countries. Self-reporting leads to overestimating RA.

Background: Genetic and environmental backgrounds influence the development of rheumatoid arthritis (RA) and its frequency has regional variations. In Latin America epidemiologic data are scarce. Objectives: We aimed to determine the prevalence of RA in Chile as part of the National Health Survey (ENS, Encuesta Nacional de Salud). Methods: ENS was a cross-sectional household survey with a stratified multistage probability sample of 6,233 participants performed between August 2016 and March 2017. A screening instrument for RA was applied to a random sample of 3,700 subjects >30 years old.1, 2 Positive screening was defined by at least one of the following: (i) 2 swollen joints for at least 4 consecutive weeks (past or present) and/or (ii) a diagnosis of arthritis in the past. Individuals with positive screening had Rheumatoid Factor, Anti-citrullinated protein antibodies, and C-reactive protein measured and clinical examination was performed by a rheumatologist. Self-report of doctor-diagnosed RA was also performed. Results: The screening questionnaire was applied to 2,998 subjects. Seven hundred and thirty-eight (22.1%) had a positive screening. Among the subjects with a positive screening 493 (66%) had consulted a rheumatologist. Thirty-one subjects had RA according to the ACR/EULAR 2010 classification criteria, which corresponds to 0.6% (95%CI 0.3, 1.2). Three point three per cent reported having RA. Prevalence was higher in women and in high SES. Conclusion: According to this national population-based study RA prevalence in Chile is 0.6% (0.3, 1.2). This is similar to the prevalence previously reported in developed countries, which is noteworthy given the differences in sociodemographic characteristics which exist compared to Chile. Self-reporting leads to an important overestimation of RA. Our study suggests there is a higher risk of RA in subjects with high SES in this region. References [1] MacGregor AJ, Riste LK, Hazes JMW, Silman AJ. Low prevalence of rheumatoid arthritis in Black Caribbeans compared with Whites in inner city Manchester. Ann Rheum Dis 1994;53:293–7 [2] Carmona L, et al. The prevalence of rheumatoid arthritis in the general population of Spain. Rheumatology (Oxford). 2002;41(1):88-95. Disclosure of Interests: josefina duran: None declared, loreto massardo Speakers bureau: Werfen, carolina llanos: None declared, sergio iacobelli: None declared, Paula Burgos: None declared, Raquel Aguilera: None declared, maria eugenia martinez: None declared, marcela cisternas: None declared, macarena armstrong: None declared, mirentxu iruretagoyena: None declared, francisco radrigan: None declared, alvaro passi: None declared, pablo riedemann: None declared, camila cifuentes: None declared, lucero hagedorn: None declared, natalia crisostomo: None declared, alvaro cisternas: None declared, paula margozzini: None declared