B-191 Celiac Disease: A Laboratory Diagnostic Approach Based on Immunological Markers

Abstract Background Celiac disease is a chronic, systemic autoimmune disorder with a strong genetic predisposition, triggered by the ingestion of gluten-containing cereals such as wheat, barley, and rye. The disease exhibits a wide spectrum of clinical manifestations, ranging from classical gastrointestinal symptoms to extraintestinal and asymptomatic forms, and is characterized by significant immunological and histopathological heterogeneity. This variability contributes to frequent underdiagnosis and diagnostic delay, particularly in non-classical and potential forms of the disease. Consequently, the identification and interpretation of reliable, accessible, and non-invasive diagnostic tools remain a challenge in clinical practice. This study aimed to evaluate the laboratory diagnostic profile associated with gluten exposure by comparing food reactivity tests with immunological markers traditionally used in the diagnosis of celiac disease, with particular emphasis on gluten-containing foods. Methods An observational, analytical, cross-sectional study with a quantitative approach was carried out. A total of 36 patients who underwent food intolerance testing by immunoblot (IA200 MyFoodProfile Advanced 1, Euroimmun) between August and December 2025 were included. Data were obtained from a laboratory in São Paulo, Brazil. Immunological evaluation included anti-endomysial antibodies measured by indirect immunofluorescence, and anti-gliadin and anti–tissue transglutaminase antibodies (IgA and IgG), measured by ELISA methods, all performed using Euroimmun assay platforms. RAST(IgE) was also performed for six gluten-containing foods, including wheat flour, buckwheat flour, wheat semolina, rye, and oats, using chemiluminescence (Immulite 2000 System SPE and TIE / Siemens®). Statistical analyses were performed using SPSS Statistics version 31.0, with associations assessed by chi-square or Fisher’s exact tests, adopting a significance level of 5%. Results Among the 36 analyzed cases, 6 (16.2%) demonstrated positive reactivity to gluten, and 17 (47.2%) were positive for gluten-containing foods, with heterogeneous patterns and varying intensities. One individual (2.7%) exhibited strong reactivity to all tested gluten-derived flours despite negative celiac-specific serology, suggesting non-autoimmune mechanisms. Moderate reactivity to wheat flour and rye was observed in two cases (5.4%), while the remaining cases showed selective reactivity to specific cereals. Anti-endomysial antibodies and anti–tissue transglutaminase antibodies (IgA and IgG) were non-reactive in 100% of patients. Anti-gliadin IgA was positive in 3 (8.3%), and anti-gliadin IgG in 1 (2.7%) of cases. Only one individual (2.7%) presented positive RAST (IgE) results (>10 kU/L) for all tested gluten-containing foods, indicating an IgE-mediated allergic response. No statistically significant association was observed between food reactivity tests and celiac disease specific immunological markers (p > 0.05). Conclusion Laboratory reactivity to gluten and gluten-containing foods did not correlate with autoimmune markers compatible with celiac disease. Although food reactivity tests may assist in dietary guidance and symptom management, they should not be considered diagnostic for celiac disease. Serological assays remain essential for differentiating celiac disease from non-celiac gluten sensitivity, food intolerance, and IgE-mediated food allergy, emphasizing the importance of integrated interpretation of laboratory findings.