Bronchial hyper-responsiveness predicts the development of mild clinical asthma within 2 yr in school children with hay-fever.

In children with mild asthma, symptoms are not always apparent. Therefore, results of tests play an important role for the diagnosis. First, to investigate whether children with bronchial hyper-responsiveness (BHR) but no symptoms of asthma in 1992 had developed clinical asthma at follow up in 1994. The second aim was to find out the diagnostic properties of tests for asthma/allergic inflammation, using either doctor diagnosed asthma (DDA), self-assessed symptoms of asthma or iso-capnic hyperventilation of cold air (IHCA), as the standard, to diagnose asthma in a group of children with hay fever. Twenty-eight children with pollinosis, 12 of them with a history of asthma for the first time during the season 1992, were studied during the birch pollen season and in the autumn of 1994. During both periods, the bronchial hyper-reactivity was estimated by methacholine bronchial provocation tests (MBPT), bronchial variability by peak expiratory flow rate variability, subjective symptoms of asthma by visual analogue scale (VAS) and bronchial inflammation by serum and urine levels of inflammatory mediators. In 1994 IHCA was added during both seasons. Eight of 16 children with BHR but without clinical asthma in 1992 had developed asthma in 1994, 14 of 16 reacted to IHCA and 13 to MBPT. All 12 children with DDA in 1992 had still asthma in 1994 and 14 children with BHR in 1992 had persistent BHR in 1994. Of 23 children with BHR in 1992, 17 had DDA in 1994 and all maintained their BHR. Furthermore, 20 of them reacted to IHCA in 1994. In 1994, 24 of 28 hay-fever children had a positive IHCA tests and 24 had positive MBPT. In relation to VAS, the sensitivity of IHCA and MBPT to predict present asthma was high, but the specificity low, whereas the specificity of most other tests was high, but based on few individuals. In relation to DDA both the IHCA test (65-80%) and the MBPT test (79-85%) had a high sensitivity and it was three to six times more likely to find a positive test among asthmatics than in non-asthmatics. Children with hay fever without clinical asthma have a high risk of developing asthma within 2 yr. In relation to DDA, inhalation of cold air and the MBPT showed a high sensitivity.