Screening for childhood asthma using an exercise test.

BACKGROUND Screening for asthma in children in the community could have advantages at a time when prevalence rates of the condition and associated hospital admission rates are rising. AIM The aim of this study was to assess the usefulness of a standard exercise test as a marker of asthma or potential asthma in children, and to examine the relationship between asthma and other respiratory tract illnesses. METHOD In 1985 a cross-sectional research study was undertaken in 10 primary schools in West Glamorgan; the children were followed up over six years until 1991. The exercise test involved measuring peak expiratory flow rate before and after the children ran as fast as they could for six minutes. A control group of children with a negative exercise test result were compared with those not known to have asthma who had a positive result (fall in peak expiratory flow rate of 15% or greater), using clinical data. Similar clinical comparisons were undertaken between the children known to have asthma and a control group. RESULTS Of 864 children not known to have asthma, 60 had a positive exercise result. Of 92 children known to have asthma, 33 had a positive test result and seven were unable to finish the test because of bronchospasm, a sensitivity of 43% and a specificity of 93%. Follow up of 55 of the 60 children not known to have asthma but who had an abnormal response to the test showed that 32 had developed clinically recognizable asthma six years later. There was a significantly higher prevalence of atopic and respiratory illnesses (otitis media, hay fever and eczema) in the group of children with bronchial hyperreactivity demonstrated on exercise than in those without bronchial hyperreactivity. CONCLUSION This research shows that bronchial hyperreactivity demonstrated by an exercise test can be a marker for childhood asthma. The study has also identified other respiratory tract illnesses which appear to belong to the same spectrum as asthma.