Prevalence of positive coeliac disease serology and HLA risk genotypes in a multiethnic population of adults in Canada: a cross-sectional study

OBJECTIVES: Coeliac disease (CD) is a complex autoimmune disorder with known genetic risk factors. Approximately 1% of individuals of European ancestry have CD, but the prevalence among different ethnicities living in Canada remains unknown. The objective of the present study was to determine the prevalence of positive CD serology in a population of Canadian adults living in Toronto, and to determine whether the prevalence of CD seropositivity and predisposing human leucocyte antigen (HLA)-DQ2/DQ8 risk genotypes differ between major ethnocultural groups. DESIGN: Cross-sectional screening study of participants from the Toronto Nutrigenomics and Health and the Toronto Healthy Diet studies. SETTING: University campus and households across Toronto, Canada. PARTICIPANTS: FREE-LIVING: Adults (n=2832) of diverse ethnocultural backgrounds. MAIN OUTCOME MEASURES: Prevalence of positive CD serology was determined by screening for antitissue transglutaminase antibodies in individuals with predisposing HLA-DQ2/DQ8 genotypes. HLA genotypes were determined using six single nucleotide polymorphisms in the HLA gene region. RESULTS: Of the 2832 individuals screened, a total of 25 (0.88%; 95% CI 0.57% to 1.30%) were determined to have positive CD serology. The majority of seropositive CD cases were undiagnosed (87%). Prevalence was highest among Caucasians (1.48%; 95% CI 0.93% to 2.23%), and similar in those of ‘Other’ (0.74%; 95% CI 0.09% to 2.63%) or ‘Unknown’ (0.43; 95% CI 0.01% to 2.36%) ethnicity. No cases of positive CD serology were identified among East Asian or South Asian individuals. East Asians had a lower prevalence of HLA risk genotypes than Caucasians and South Asians (p<0.005). CONCLUSIONS: The prevalence of positive CD serology among Canadian adults living in Toronto is likely ~1%, with 87% of cases being undiagnosed. These findings suggest the need for better screening in high genetic risk groups. TRIAL REGISTRATION NUMBER: NCT00516620; Post-results.