Underestimation of specific IgE measurements using extract-based assays on undiluted sera revealed through dilution

The measurement of specific IgE (sIgE) to foods is an established clinical tool for the diagnosis and management of allergic disease.1 Normally, sIgE is measured using undiluted serum, and assays are only performed at a dilution if the value is greater than or equal to 90 international units (IU)/mL. [...]when serum gives sIgE values of less than or equal to 50 IU/mL, the possibility that the value is a significant underestimate is rarely considered. [...]manipulating the amount of allergen on the solid phase, such that there is an imbalance in antibody and allergen concentrations, can markedly change the measured sIgE values. Component tests, if available, are one option, but simply doing a dilution may be equally helpful to identify the presence of a minor allergen.Methods Assays for sIgE to α-gal were performed by coupling biotinylated cetuximab to a streptavidin solid phase.E1 Sera from patients with EoE who were positive for sIgE to Dermatophagoides pteronyssinus and cat dander extract were assayed for sIgE to 112 molecular allergens by Immuno Solid-Phase Allergen Chip (ISAC) to determine the dominant sensitization. Patient Allergen extract sIgE in undiluted sample (IU/mL) sIgE in 1:8 sample, calculated (IU/mL) Percentage difference Dominant allergen Results where the dominant allergen represents a significant proportion of the extract...