Abstract

Background International comparative data on autoimmune gastritis (AIG) remain limited. Objective We aimed to describe AIG features and quantify the risk of gastric adenocarcinoma and type 1 gastric neuroendocrine tumours (NETs). Design Retrospective study across eight tertiary centres in Europe, T & uuml;rkiye, Latin America, the USA and Japan. Adults with histologically confirmed AIG were included. Clinical and follow-up data were collected to estimate adenocarcinoma and NET incidence and associated factors. Results 1240 patients were included (female:male 2:1; median age 59, IQR 48-67; median follow-up 68 months, IQR 36-108). Macrocytic anaemia predominated in Europe (45.6%), microcytic anaemia in T & uuml;rkiye (56.1%) and Latin America (64.7%). Autoimmune comorbidities were most frequent in Latin America (67.7%). 36 (2.9%) gastric adenocarcinomas and 132 (10.6%) NETs occurred. No incident adenocarcinomas were reported in Latin America or Japan cohorts. Crude incidence rates ranged from 1.15 to 1.47 for adenocarcinoma and 0.70 to 1.62/100 person-years for NETs. Factors associated with adenocarcinoma included age >65 years (OR 4.50, 95% CI 2.18 to 9.27), intestinal metaplasia (OR 1.51, 95% CI 1.16 to 1.97), gastrin-17 >1316 pg/mL (OR 15.52, 95% CI 3.61 to 66.71) and prior proton pump inhibitor (PPI) (OR 5.74, 95% CI 2.13 to 15.47). For NETs, prior PPI (OR 2.69, 95% CI 1.12 to 6.46), smoking (OR 2.45, 95% CI 1.75 to 3.42), intestinal metaplasia (OR 2.88, 95% CI 1.38 to 6.01) and gastrin-17 >1316 pg/mL (OR 3.25, 95% CI 1.42 to 7.45), were associated with higher odds, while Helicobacter pylori eradication was associated with lower odds of NETs (OR 0.25, 95% CI 0.07 to 0.88). Conclusion AIG presentation and neoplastic risks differ by region, warranting further research and potentially region-specific follow-up strategies.