Between Oral Food Challenges (OFC) and skin prick tests, allergies are tested in patients where an immune-allergic reaction is present. And for further and more accurate testing, the presence of allergen-specific serum IgE antibodies is studied through in vitro testing. This test is limited because it cannot differentiate between allergy and sensitization. Another in vitro test is the basophil activation test (BAT), which is an assay that assesses the degree of IgE activation after exposure to a stimulus. It increases specificity for better results. And a final in vitro test is the sIgG4, which is found to be unconventional.
IgE serum in vitro testing detects allergen-specific IgE levels, using a little amount of that serum that can be stored in labs. The sIgE levels are reliable biomarkers that predict the seriousness of food allergies; however, it shows low specificity in diagnosing them. Thus, an additional molecular allergology is performed in some cases e.g., when a homology of molecules is detected. BAT evaluates the percentages of activated basophils after the binding of IgE antibodies with their receptors. BAT showed better accuracy than other tests, presenting high sensitivity, specificity, and +ve/-ve predictive values. It also determines the intensity of the allergy in the patient. Finally, concerning the serum IgG4, a study was done on three groups of allergic, healthy, and a control group. No variation of sIgG4 was detected among them, which determines that these are released only due to an extended acquaintance with food antigens.
In conclusion, specific IgE in vitro tests is the most convenient in diagnosing allergies in patients. BAT is a unique approach that distinguishes intense forms of allergens and predicts food allergies due to its high specificity. It was found that sIgG4 in vitro test is redundant for diagnosis.
Ref: https://onlinelibrary.wiley.com/doi/full/10.1111/pai.13342
