Association of allergy, atopic history and eosinophilia with AHR
Several studies have identified a personal history of having an allergy to various antigens as a risk factor for AHR(3, 12-14). Tree pollen, especially, has been described as an important allergen in this context(15), while no association could be verified in relation to mold sensitization(15, 16). In accordance with previous studies, we found an association of AHR with general skin test positivity as well as with sensitization to most aeroallergens, except mold, and where tree pollen sensitization reached the highest significance level. This high significance might be due to the specific local environment. The birch tree is widely spread in Germany and has emerged as a common allergen in children with allergic rhinitis and asthma(17).
In contrast, in an earlier study including children who were also without an obstructive pattern, no significant relationship between personal allergy and the presence of AHR was detectable(7). However, unlike the earlier study, in the present study patients with predominantly exercise-induced symptoms were excluded. The symptoms of the patients in our study group occurred mainly when they were at rest and were frequently triggered by allergens. Thus, it can be assumed that in the present study there are more patients with allergies, supported by the higher percentage of sensitized children compared with the previous study (51.2% vs 43.6%). Correspondingly, a stronger association between allergy and AHR can be expected. Especially in atopic patients, the MCC is accepted as a highly sensitive tool to detect AHR(18).
A family history of atopy has also been described by some authors as associated with AHR(19, 20), while others could not confirm such a relationship(21). Although our data did not show a significant relationship of atopic family history with AHR, co-existence of two or more atopic diseases in the family nearly reached significance. In general, it is difficult to evaluate the influence of a genetic history because subjective measures might lead to overestimating the risk from family history. So it can be assumed that parents suffering from respiratory symptoms would be more likely to recognize symptoms in their children and consult a physician(21, 22).
In accordance with the results of previous studies, we identified an association between high eosinophilia counts and AHR(7, 14, 23). Unfortunately, our database of eosinophilia was incomplete, therefore it was not included in the multivariate analysis.