Esophagus to Small Intestine
Variation in testing for and incidence of celiac autoimmunity in Canada: A population-based study
Background and aims: The incidence of biopsy-confirmed celiac disease has increased. However, few studies have explored the incidence of celiac autoimmunity based on positive serology results.
Methods: A population-based cohort study assessed testing of tissue transglutaminase antibodies (tTG-IgA) in Alberta from 2012 to 2020. After excluding prevalent cases, incident celiac autoimmunity was defined as the first positive tTG-IgA result between 2015 and 2020. Testing and incidence rates for celiac autoimmunity were calculated per 1000 and 100,000 person-years, respectively. Incidence rate ratios (IRRs) were calcu-lated to identify differences by demographic and regional factors. Average annual percent changes (AAPCs) assessed trends over time.
Results: The testing rate of tTG-IgA was 20.2 per 1000 person-years and remained stable from 2012 to 2020 (AAPC, 1.2%; 95% confidence in-terval [CI]: -0.5–2.9). Testing was higher in female patients (IRR = 1.66; 95% CI: 1.65−1.66), those living in metropolitan areas (IRR = 1.39; 95% CI: 1.38−1.40), and in areas of lower socioeconomic deprivation (lowest compared to highest IRR = 1.24; 95% CI: 1.23−1.25). Incidence of celiac autoimmunity was 33.8 per 100,000 person-years and increased from 2015 to 2020 (AAPC, 6.2%; 95% CI: 3.1−9.5). Among those with tTG-IgA results ≥ 10 times the upper limit of normal, the incidence was 12.9 per 100,000 person-years. The incidence of celiac autoimmunity was higher in metropolitan settings (IRR = 1.28; 95% CI: 1.21−1.35) and in the least socioeconomically deprived areas compared to the highest (IRR = 1.22; 95% CI: 1.14−1.32).
Conclusions: Incidence of celiac autoimmunity is high and increasing, despite stable testing rates. Variation in testing patterns may lead to un-der-reporting the incidence of celiac autoimmunity in non-metropolitan areas and more socioeconomically deprived neighborhoods.