Before we could examine interlaboratory results of food allergy testing, intralaboratory reliability needed to be evaluated. Good intralaboratory reproducibility means that when a sample is compared with itself (as in a split sample), the results are expected to be identical. Similarly, when a person maintains a normal dietary routine over the course of a week, the results of a food allergy test would be expected to be the same. In this study, the cell size variability method delivered very different results for all the samples submitted, and therefore had no internal reproducibility or accuracy. The IgG ELISA method had excellent intralaboratory correla-tion for the split sample and the samples analyzed over the course of a week. The unreliability of the cell size variability method results prevented an interlaboratory analysis comparing the results of the cell size variability method to the IgG ELISA method.
Other researchers have compared allergy testing methods, although most studies focus on IgE-related allergies as opposed to IgG-mediated responses. Double-blind placebo-controlled food challenge (DBPCFC) is considered the gold standard in food allergy testing and is strongly correlated with IgE testing. In this type of testing, the reaction of a suspected allergenic food is compared to a placebo food, known to not evoke a response. Foods that are known to induce anaphylaxis are not generally tested. The DBPCFC identifies foods that evoke immediate food allergy symptoms. Skin tests can also be used to identify food allergens. These tests are more sensitive than IgE blood tests.
IgE to food allergens demonstrates an immediate phase immune response. Delayed type responses, however, are not mediated by IgE anti