IGHE and Allergy: ROC curve analysis was carried out to assess the diagnostic value of total IgE in multiple allergies in two clinical situations: (a) in patients with an unknown allergic status (AUC = 0.762 (95% CI = 0.726–0.799), p < 0.001) and (b) in patients already known as allergic for one allergen (AUC = 0.636 (95% CI = 0.588–0.684), p < 0.001) (Figure 3).