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In this article, rheumatoid arthritis (RA) prevalence based on a self-reported survey (CARTaGENE) was 2.9% (564 out of 19,704 patients) with a 95% CI of 2.6-3.1 before misclassification adjustment. This estimate would constitute the highest RA prevalence reported in the world since 1980, followed by Cuba (2.7%) in 2000 2 , Finland in 1989 3 , and Australia in the National Health Survey (1.9%) in 2014-2015 4. Despite a large sample size that closely resembled the general population in Canada 5 , it is much higher than the database-estimated prevalence by Lacaille, et al (0.8%) 6 , Widdifield, et al (0.9%) 7 , or Jean, et al (0.8%) 8. This estimate is highly biased for the reason that self-reported diagnosis of RA is not sufficient for the ascertainment of RA cases without clinical verification. It is an unreliable method for research or clinical purposes in various populations, because of the low percentage (21-34%) of people who will have confirmed RA 9,10. Our concerns are about the validity of selfreported data in the CARTaGENE study to estimate the RA prevalence in Quebec (Canada), without clinical verification by a doctor or by using any RA classification criteria.