Association Between Tissue Transglutaminase IgA Levels and Villous Atrophy in Pediatric Celiac Disease: A Retrospective Cross-Sectional Study

Objective: The 2020 European Society for Paediatric Gastroenterology, Hepatology and Nutrition no-biopsy algorithm for celiac disease (CD) requires a tissue transglutaminase IgA (tTG-IgA) level ≥10× the upper limit of normal (ULN) plus endomysial antibody IgA (EMA-IgA) positivity on a second sample.This study evaluated the diagnostic performance of the tTG-IgA ≥10× ULN threshold for predicting Marsh grade 3 histology at a center where EMA-IgA testing was not routinely available.Methods: This retrospective study included pediatric patients who underwent duodenal biopsy for suspected CD between January and December 2023 at Şanlıurfa Training and Research Hospital.Patients were categorized as tTG-IgA <10× ULN or ≥10× ULN.Sensitivity, specificity, predictive values, accuracy, and Cohen's kappa were calculated using Marsh grade 3 as the reference standard.Factors associated with Marsh grade 3 were assessed using univariable logistic regression.Results: Of 141 patients, 108 (76.6%) had tTG-IgA ≥10× ULN and 130 (92.2%) had Marsh grade 3 histology.Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy for the threshold were 78.5%, 45.5%, 94.4%, 15.2%, and 75.9%, respectively.Agreement with Marsh grade 3 was low [κ=0.125;95% confidence interval (CI), -0.040 to 0.290; p=0.072].Any bulbar or distal duodenal endoscopic abnormality was associated with Marsh grade 3 (odds ratio =11.810; 95% CI, 2.697-51.703;p=0.001).Conclusion: At our institution, without routine EMA-IgA testing, tTG-IgA levels ≥10× ULN had high PPV for advanced histological injury; however, this marker alone was insufficient as a no-biopsy diagnostic criterion.