• Christine van Dalen, Elizabeth Harding, Jill Parkin, Soo Cheng, Neil Pearce, and Jeroen Douwes.
• Centre for Public Health Research, Research School of Public Health, Massey University, Wellington, New Zealand. c.j.vandalen@massey.ac.nz
• Arch Pediatr Adolesc Med. 2008 Dec 1; 162 (12): 1169-74.

ObjectiveTo determine whether lung function alters asthma severity based on symptom history in asthmatic adolescents.DesignData on asthma symptoms and lung function were collected from adolescents randomly selected from the general population.SettingFive schools from the central Wellington, New Zealand, area during 2003 to 2005.ParticipantsTwo hundred twenty-four secondary school students aged 13 to 17 years (asthmatic, 118; nonasthmatic, 106).Main ExposuresAsthma questionnaire and lung function testing.Main Outcome MeasuresDistribution of asthmatic adolescents in each severity class based on symptoms, lung function, or a combination of both.ResultsMedian values for all spirometric parameters for asthmatic adolescents, apart from forced expiratory volume in the first second of expiration (FEV(1))/forced vital capacity (FVC), were in the normal range. Distribution of severity (based on symptoms and beta(2)-agonist use with adjustment for regular inhaled corticosteroid use) was 48.3%, mild; 28.8%, moderate; and 22.9%, severe asthma. For severity based on percentages of predicted FEV(1) and predicted forced expiratory flow, midexpiratory phase (FEF(25%-75%)) and FEV(1)/FVC, the percentages were 89.8%, 86.4%, and 63.5%, mild; 9.3%, 10.2%, and 18.6%, moderate; and 0.9%, 3.4%, and 17.8%, severe asthma, respectively. When percentages of predicted FEV(1) or predicted FEF(25%-75%) or FEV(1)/FVC were added to symptom severity, 6.8%, 5.1%, and 16.9% of asthmatic adolescents were reclassified into another severity group, respectively.ConclusionsThe majority of asthmatic adolescents have normal lung function despite experiencing significant asthma symptoms. Adding FEV(1)/FVC to symptom history changes the distribution of severity; however, both percentages of predicted FEV(1) and FEF(25%-75%) have little added effect in assessing asthma severity in adolescents.

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