A potential role of gliadin extract skin prick test in IgE-mediated wheat allergy

BACKGROUND: Wheat extracts containing both water/salt and alcohol soluble proteins may increase extract's accuracy for diagnosing IgE-mediated wheat allergy. OBJECTIVE: This study aimed to determine the performance of new invented in-house prepared wheat extracts for skin prick test (SPT). METHODS: Children aged 1-18 years with history of immediate wheat allergy were recruited. Four in-house prepared wheat extracts (wheat-Coca-10%EtOH, and 3 new invented extracts, wheat-salt, gliadin, and glutenin) and a commercial wheat extract were used for SPT. Serum specific IgE (sIgE) to wheat and omega-5 (ω-5) gliadin were also determined. Oral food challenge (OFC) with wheat flours was performed in all patients except those with history of wheat-induced anaphylaxis or with recent symptoms within the past 6 months. RESULTS: Thirty-one children were recruited. Of those, 14 were excluded from OFC (12 with history of anaphylaxis and 2 with recent symptom). OFC was positive in 8 of 17 children. Of the 5 extracts and sIgE to wheat and ω-5 gliadin, gliadin extract provided the best SPT performance with 84.2% sensitivity, 88.9% specificity, 94.1% positive predictive value (PPV), 72.7% negative predictive value (NPV), 7.59 positive likelihood ratio (LR), 0.18 negative LR, and 85.7% accuracy. CONCLUSIONS: Compared to other in-house and commercial wheat extracts and sIgE to wheat and ω-5 gliadin, SPT with an in-house gliadin extract yielded the highest performance for the diagnosis IgE-mediated wheat allergy.