IGHE and allergic disease: To investigate the capability of serum total IgE to discriminate children with and without atopy and allergic diseases in this population, we specifically compared three potential reference values: (1) 77.7 kU/L (the optimal cutoff on the ROC curve), (2) 164.3 kU/L (the upper 95% CI in 564 non-atopic subjects) and (3) 100 kU/L (a customary cutoff that is commonly used in clinical practice) [2,3].