High prevalence of ultra‐short celiac disease in children with low anti‐tissue transglutaminase immunoglobulin A levels: The risk of misdiagnosis without bulb biopsy

OBJECTIVES: Despite recent advances in diagnostics, celiac disease (CD) diagnosis remains challenging. Ultra-short celiac disease (USCD) has been proposed as a distinct phenotype characterized by villous atrophy confined to the duodenal bulb, positive celiac serology, and clinical features consistent with CD. This study aimed to assess the impact of adherence to European Society for Pediatric Gastroenterology, Hepatology and Nutrition guidelines, including duodenal bulb biopsy, in the diagnostic process of CD, and to investigate whether omission of bulb sampling may have led to misclassification of potential celiac disease (PCD). METHODS: We conducted a retrospective, observational study of pediatric patients evaluated for CD between June 2017 and December 2024 at a tertiary-care center. Patients undergoing biopsy-based diagnosis were stratified by biopsy protocol: distal duodenum (DII) versus distal duodenum plus bulb (DII + Bulb). A logistic regression model using tissue transglutaminase immunoglobulin A (TTG-IgA) levels as predictor estimated the likelihood of missed USCD among PCD cases in the DII group. RESULTS: Out of 474 patients undergoing endoscopy, 361 had TTG-IgA <10 × ULN. Of these, 24 were in DII group and 337 in DII + Bulb group. In the latter, 140 (41.5%) were classified as classic CD, 54 (16%) as PCD, and 143 (42.4%) as USCD. PCD detection dramatically dropped after full adherence to guidelines. The logistic model identified seven of nine PCD patients in DII group as likely USCD. CONCLUSIONS: Systematic duodenal bulb biopsy significantly improves USCD detection in patients with low TTG-IgA levels. PCD cases diagnosed without bulb sampling warrant reassessment, especially during transition to adult care.