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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

Hereditary periodic fever syndromes (HPFS) are rare genetic diseases characterized by recurrent episodes of inflammation. Little information is available concerning HPFS in Latin American Hispanic population. The purpose of this study was to determine the clinical and genetic features of HPFS in Chilean population. A multicenter retrospective study of Hispanic Chilean patients with genetically confirmed HPFS was performed. We included 13 patients, 8 with familial Mediterranean fever (FMF) and 5 with TNF receptor-associated periodic syndrome (TRAPS), evaluated at rheumatology or pediatric rheumatology clinics between January 2007 and December 2010. Median age of symptoms onset was 8 years (range 1-35) and 8 years (range 0.3-21) for FMF and TRAPS, respectively. Median duration of fever was 3 days (range 2.5-15) for FMF and 21 days (range 9.5-30) for TRAPS. Genotyping of the MEFV gene in FMF patients revealed a homozygous M694V missense mutation in one patient, and heterozygous missense mutations in seven patients: M694V (n = 3), E148Q, R717H, A744S, and A511V. Sequencing of the TNFRSF1A gene in TRAPS patients revealed heterozygous missense mutations in four patients: T50M, C30R, R92Q, and IVS3+30:G -> A, and a two-base pair deletion (IVS2-17_18del2bpCT) in one patient. Mutation in MEFV R717H and mutations in TNFRSF1A IVS2-17_18del2bpCT and IVS3+30:G -> A are novel and have not been described previously. This study reports the largest series of genetically confirmed HPFS in Latin America, and adds evidence regarding the clinical and genetic characteristics of patients with FMF and TRAPS in Hispanic population. Mutations identified in MEFV and TNFRSF1A genes include defects reported in other ethnicities and novel mutations.