INTRODUCTION
In Europe, the prevalence of allergic asthma (8%) and rhinitis (25%) is high with still increasing trend in the last decades.1
The diagnosis of pollen allergy used to be mainly based on medical history, skin prick test (SPT) and the detection of allergen-specific serum IgE by using pollen extracts. Pollen seasons from distinct plants may overlap, and pan-allergens contained in various pollen may cause IgE-cross-reactions, though. Therefore, molecular allergy diagnosis (MD) assessing IgE reactivity to so-called marker allergens has increasingly gained importance in recent years. However, the question whether MD may improve extract-based diagnosis and help with the decision for allergen-specific immunotherapy (AIT) has not been clarified yet.2,3
More than 90% of patients with grass pollen allergy show IgE antibodies against Phl p 1 and Phl p 5,4 and more than 95% of birch allergic patients are sensitized to the major allergen Bet v 1.5 Ash tree is another allergen of increasing relevance in Central-Europe.6 The distinction between birch and ash tree allergy is relevant for the decision which AIT is suitable. However, both pollen seasons overlap in Austria causing concomitant allergic symptoms to either tree species.8In MD the structurally homologous Ole e 1 from olive tree is usually used instead of the major ash tree allergen Fra e 1 which is not commercially available.7
The defensin-like protein Art v 1 is the single major allergen in mugwort pollen, recognized by IgE antibodies from 90% of patients with mugwort allergy.9 About 10-14% of patients with rhinoconjunctivitis in Eastern Austria suffer from mugwort allergy.10 With the mugwort season in eastern Austria overlapping with that of the ragweed season, differentiation based exclusively on patients’ history is difficult.8Ragweed has gained increasing interest, not only in Eastern, but also in Central Europe. The major allergen available for genuine ragweed allergy is Amb a 1, a pectate lyase with about 50% sensitization rates in ambrosia allergic patients.11
Cross-reactivity between mugwort and ragweed extract often leads to inconclusive results. For example, Amb a 1 and Art v 6 as well as Amb a 4 and Art v 1 show structural homologies,12 however, only Amb a 1 and Art v 1 offer clinical importance for pollen allergic patients. Also, in this case it is important to discriminate between both weed allergies, especially if one has to decide which AIT has to be applied.
The aim of this study was to evaluate whether the use of the major pollen-allergens (Phl p 1+5, Bet v 1, Ole e 1, Art v 1, Amb a 1) can increase the diagnostic accuracy in patients with a single-sensitization against grass, birch, ash, mugwort or ragweed pollen. If there was a discrepancy in the results of extract and major-allergen, we reviewed medical charts to see if this knowledge changed medical recommendations for AIT.
In addition, we intended to analyze how many patients were double-sensitized to birch and ash-tree and/or to mugwort and ragweed, respectively and if this double-sensitization was caused by extracts´ cross-reactivity or was based on a relevant sensitization against one or both major allergens.
The study was part of a diploma thesis (C.H.) at the Medical University Vienna, Austria.13