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Christine van Dalen, PhD; Elizabeth Harding, RN; Jill Parkin, RN; Soo Cheng, BSc(Hons); Neil Pearce, PhD; Jeroen Douwes, PhD

Arch Pediatr Adolesc Med. 2008;162(12):1169-1174.

Objective  To determine whether lung function alters asthma severity based on symptom history in asthmatic adolescents.

Design  Data on asthma symptoms and lung function were collected from adolescents randomly selected from the general population.

Setting  Five schools from the central Wellington, New Zealand, area during 2003 to 2005.

Participants  Two hundred twenty-four secondary school students aged 13 to 17 years (asthmatic, 118; nonasthmatic, 106).

Main Exposures  Asthma questionnaire and lung function testing.

Main Outcome Measures  Distribution of asthmatic adolescents in each severity class based on symptoms, lung function, or a combination of both.

Results  Median values for all spirometric parameters for asthmatic adolescents, apart from forced expiratory volume in the first second of expiration (FEV₁)/forced vital capacity (FVC), were in the normal range. Distribution of severity (based on symptoms and β₂-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 FEV₁ and predicted forced expiratory flow, midexpiratory phase (FEF_25%-75%) and FEV₁/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 FEV₁ or predicted FEF_25%-75% or FEV₁/FVC were added to symptom severity, 6.8%, 5.1%, and 16.9% of asthmatic adolescents were reclassified into another severity group, respectively.

Conclusions  The majority of asthmatic adolescents have normal lung function despite experiencing significant asthma symptoms. Adding FEV₁/FVC to symptom history changes the distribution of severity; however, both percentages of predicted FEV₁ and FEF_25%-75% have little added effect in assessing asthma severity in adolescents.

Author Affiliations: Centre for Public Health Research, Research School of Public Health, Massey University, Wellington, New Zealand.

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