Pitfalls in the diagnosis of house dust mite allergy

Abstract

House dust mite (HDM) is the most significant indoor allergen, responsible for not only many cases of rhinoconjunctivitis but also for many cases of bronchial asthma, rendering it of considerable socioeconomic relevance. Besides symptomatic treatment and avoidance measures, allergen immunotherapy (AIT) is crucial, as the only causal, disease-modifying therapeutic approach. However, high diagnostic certainty is essential for initiating AIT. The challenge in making acorrect diagnosis lies in interpreting the demonstrated HDM sensitization regarding its clinical relevance (clinically silent sensitization vs. allergy). While the risk of allergy increases with the level of IgE titers against HDM extract, Der p1, or Der p2, as well as with the breadth of the molecular sensitization profile against HDM components (Der p1, Der p2, Der p23), no threshold can be defined for the presence of allergy, nor can sensitization to aspecific component be confidently considered allergy inducing. It should be noted that at least in Southern Bavaria, the prevalence of Der p23 sensitization is too low to be considered amajor allergen, and Der p23 is not able to molecularly differentiate all HDM sensitizations when added to the two major allergens Der p1 and Der p2. Evidently, HDM possesses adiverse profile of allergens, with some relevant ones possibly yet to be described. Unfortunately, patient history does not provide asufficient assessment of the clinical relevance of ademonstrated HDM sensitization, necessitating allergen provocation testing before initiating AIT with HDM, despite the relatively large effort involved.