Background: To describe the clinical characteristics of school children with hay-fever based on baseline data from the PAT-Study.
Material: Two hundred and five children, 6-15 years, mean 10.7 years, with birch and or grass pollen hay-fever, without known asthma were recruited by six pediatric allergy centers in Northern and Central Europe.
Methods: Bronchial hyperresponsiveness (BHR) to methacholine tested by methacholine bronchial provocation test (MBPT) expressed in PC20 was registered during the birch and grass pollen seasons. During the winter symptoms of conjunctivitis, rhinitis and asthma were graded by visual analogue scale (VAS), conjunctival provocation test with birch and or timothy pollen extracts, skin tests with a panel of allergen extracts and MBPT were done and a questionnaire was filled in. Differences of p <0.01 level or less were considered significant.
Results: Despite the children were included because of seasonal hay-fever without known asthma, 42/205 children (21 %) got doctor diagnosed asthma (DDA) after the first season. During the three seasons, between 60 and 73 % of the children had a PC20 to methacholine ≤ 8 mg/ml, about 30 % to ≤ 2 mg/ml and 7-10% even to ≤ 0.5 mg/ml. Most children had both rhinitis and conjunctivitis. Furthermore, 119/201 children (59%) were regularly exposed to furred animals.
There was an association between DDA and the sum of VAS for asthma during the pollen seasons.
The BHR was significantly more pronounced in those with than those without DDA during all three seasons: Using the three cut offs, the difference was most pronounced during the winter season but reached also significance using the cut off limit 0.5 mg/ml during the birch pollen season.
Doctor diagnosed asthma correlated to PC20 during the seasons for most of the cut off limits for PC20 and in general there was an association in PC20 between the seasons independent of cut off limits.
Furthermore, DDA, but not BHR, correlated to exposure to traffic and there was an association between exposure to traffic and industrial pollution, but not to ETS or duration of breastfeeding.
Conclusion: The most striking feature of school children with uncomplicated hay-fever was the high frequency of DDA and BHR, most pronounced during the winter, the high frequency of exposure to living animals and sensitization to indoor allergens. Hay-fever is a generalized disease. Even without obvious asthma, BHR is common and most children have symptoms from both the eyes and the airways. Diagnosis of asthma in children with hay-fever and early anti-inflammatory treatment may improve the prognosis.