Basophil allergen threshold sensitivity: a useful approach to anti‐IgE treatment efficacy evaluation

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Abstract
Background:  Monitoring of the allergen sensitivity of a patient is most important for optimal patient care and a basic prerequisite for immunomodulating treatment. The objective of this study was to investigate how basophil allergen sensitivity can be applied in the monitoring of anti‐immunoglobulin E (IgE) treatment.Methods:  Basophils from timothy grass pollen allergic patients were, by flow cytometry, analysed for allergen threshold sensitivity (CD‐sens) by measuring CD63 up‐regulation on CD203c‐identified basophils. The results were compared with maximal percentage CD63 up‐regulation at one allergen dose (CD‐max), skin prick test end‐point allergen titration, (SPT‐sens), nasal provocation titration tests (nasal provocation titre) and serum IgE and IgE antibody concentrations.Results:  There was a significant correlation (r = 0.50, P = 0.01) between CD‐sens and SPT‐sens, CD‐sens and the IgE antibody concentration in percentage of ‘total IgE’ (relative IgE antibody concentration) (r = 0.72, P < 0.001) as well as between CD‐sens and nasal provocation titre (r = 0.54, P < 0.05) but, in contrast, CD‐max did not correlate with any of the sensitization parameters, i.e. SPT‐sens, nasal provocation titre, absolute and relative IgE antibody concentration or CD‐sens. CD‐sens could be used to monitor omalizumab treatment efficacy while, based on CD‐max, four of seven symptom‐free patients on omalizumab would have been classified as having ongoing allergy.Conclusions:  CD‐sens seems to be very useful for the determination of a patient's allergen sensitivity and should be evaluated for the measurement and monitoring of anti‐IgE treatment efficacy. CD‐max, the conventional approach to basophil allergen challenge, which mirrors cell reactivity, gives incorrect information.