269. SENSITIVITY AND SPECIFICITY OF ANTI-GLIADIN IGG ANTIBODIES FOR PATIENTS WITH GLUTEN INTOLERANCE, AND THEIR PSYCHIATRIC/PHYSICAL SYMPTOMS

Abstract Background Gluten intolerance is a syndrome characterized by several physical and psychological symptoms such as abdominal pain, constipation, diarrhea, headache, foggy brain, tiredness, anxiety, and depression, related to the ingestion of gluten. Gluten intolerance is one of the gluten-related diseases. It is thought to differ in mechanism from autoimmune diseases such as celiac disease and allergies. Although anti-gliadin IgG antibody has been presented as an immunological marker of gluten intolerance, the diagnostic criteria have not been established yet, and much remains unclear about gluten sensitivity. Hyogo Medical University has the specialized outpatient unit for gluten intolerance since 2019 to conduct medical examinations and research on gluten intolerance. We have already reported the association between treatment-resistant schizophrenia and gluten intolerance may be an aggravating factor in various psychiatric disorders. Aims & Objectives We investigated immunological gluten sensitivity in patients with subjective gluten intolerance who visited our outpatient unit for gluten intolerance and assessed their psychiatric and physical symptoms. Method From 2019 through 2024, patients with subjective symptoms of gluten intolerance aged 20-70 years who visited our outpatient unit for gluten intolerance and age- and sex-matched healthy controls without subjective symptoms of gluten intolerance were recruited. We determined immunological gluten sensitivity using anti-gliadin IgG antibody, and psychiatric and physical symptoms were evaluated by medical interview and self-administered questionnaire. We excluded participants on a strict gluten-free diet because their anti-gliadin IgG antibody levels seem to be reduced. Anti-tissue transglutaminase IgA antibody was also measured to exclude patients with celiac disease. This study was approved by the ethics committee at Hyogo Medical University. Detailed explanations of the study procedures were provided to each participant at the time we received their informed consent. Results The final sample consisted of 73 patients with subjective symptoms of gluten intolerance and 83 healthy controls participated. Among those with subjective symptoms of gluten intolerance, 26 (36%) were determined as immunological gluten sensitivity. Of the healthy controls, 11(13%) were determined as immunological gluten sensitivity. As a marker of gluten intolerance, the sensitivity and specificity of the anti-gliadin IgG antibody were 35.6% and 86.7%. Discussion & Conclusions There is a large discrepancy between subjective and immunological gluten sensitivity. Using only anti-gliadin IgG as a biomarker for gluten intolerance may not be sufficient for diagnosis. In order to establish accurate diagnostic criteria for gluten intolerance, we need more precise biomarkers or a combination of several biomarkers including anti-gliadin IgG. We also report psychiatric and somatic symptoms of gluten intolerance and immunological gluten sensitivity.