In Vitro Gliadin Challenge: Diagnostic Accuracy and Utility for the Difficult Diagnosis of Celiac Disease

OBJECTIVES: Diagnosis of celiac disease is difficult when treatment with gluten-free diet (GFD) is started before diagnosis and/or when the results of tests are inconsistent. The objective of this study was to evaluate the in vitro gliadin challenge. METHODS: The study cohort included patients without celiac disease (negative controls, n=57), patients with celiac disease (positive controls, n=166 untreated and n=55 on GFD), and patients with difficult diagnosis (n=59). All patients underwent endoscopy for collection of duodenal samples, which served for the diagnosis of celiac disease and for the in vitro evaluation of the gliadin-induced mucosal expression of seven inflammatory markers: PY99, ICAM-1 (intercellular cell adhesion molecule), HLA-DR, CD3, CD25, CD69, and transglutaminase 2 IgA. Diagnostic work-up for celiac disease included the search of specific serum antibodies. Patients of the difficult diagnosis group were asked to stop GFD for repeated search of these antibodies under untreated conditions. The area under the receptor-operated curve (ROC) was used for statistical analyses on accuracy. RESULTS: HLA-DR had the highest accuracy for celiac disease diagnosis in analyses on negative controls and positive controls also excluding patients on GFD (area under ROC=0.99). Accuracy of test did not increase combining data of HLA-DR with data of other markers. Findings were similar in the 39 patients of the difficult diagnosis group undergoing the search celiac disease-specific antibodies under untreated conditions. CONCLUSIONS: The in vitro response of mucosal HLA-DR to gliadin is an accurate tool for the diagnosis of celiac disease also in patients with difficult diagnosis.