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Adding certain spirometric measures to symptom history, beta-2-agonist use for assessing asthma severity useful, researchers suggest

Monday, December 15 2008 | Comments

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What's This? New data suggest a majority of adolescents with asthma have normal lung function even though they experience significant asthma symptoms. However, when assessing the disease, the addition of certain spirometric parameters to symptom history appears to alter severity classifications.

Researchers noted that whether or not an assessment of lung function aids in determining asthma severity remains unclear, particularly among children and adolescents. So they designed a study to explore the effect of adding lung function measures to an established assessment system that included only symptom frequency and beta-2-agonist use for classifying asthma disease severity.

The included population was comprised of 118 subjects with asthma (history of wheezing/whistling in the chest and/or any asthma medication use during the prior 12 months) and 106 without asthma, all of whom were aged 13 to 17 years and were recruited from 5 schools located in the Wellington, New Zealand, area. All of these schools had participated in the International Study of Asthma and Allergies in Childhood (ISAAC) Phase III survey of asthma symptom prevalence.

All of the participants underwent lung function testing. The spirometric parameters specifically evaluated for the study included percentage of predicted forced expiratory volume in 1 second (FEV1), FEV1/forced vital capacity (FVC), and forced expiratory flow (FEF) in the midexpiratory phase (FEF25%-75%). The main outcome measures were the distribution of the subjects with asthma in each asthma severity class based on symptoms, lung function, or a combination of both using guidelines and cutoff values from the National Asthma Education and Prevention Program Expert Panel Report 3.

The results showed that among the participants who did not have asthma, the percentages of predicted FEV1 and FVC values were close to 100%. As compared with these nonasthmatic individuals, the participants with asthma had significantly lower percentages of predicted values for FEV1 and FEF25%-75% as well as significantly lower values for FEV1/FVC, but not for percentages of predicted FVC and peak expiratory flow. However, except for FEV1/FVC, the median values for all spirometric parameters were within normal ranges for the adolescents with asthma.

Based on patient asthma symptoms and use of beta-2-agonists (adjusting for regular use of inhaled corticosteroids)--not spirometric measures--48.3% of the adolescents with asthma had mild disease, 28.8% had moderate disease, and 22.9% had severe disease. However, using predicted FEV1 or predicted FEF25%-75% to classify severity resulted in 89.8% and 86.4% having mild disease, respectively; 9.3% and 10.2% having moderate disease; and 0.9% and 3.4% having severe disease. But using FEV1/FVC to determine severity shifted a greater proportion of patients out of the mild category, with 63.5%, 18.6%, and 17.8% classified as having mild, moderate, and severe asthma. 

The researchers found that when percentages of predicted FEV1 or predicted FEF25%-75% were added to symptom severity, a respective 6.8% and 5.1% of the adolescents with asthma were reclassified into another severity group. Even more pronounced was the effect of adding FEV1/FVC to symptom severity, which led to 16.9% of the patients with asthma being changed to a different severity group.

"[I]n the vast majority of asthmatic adolescents, a single measure of percentage of predicted FEV1 or percentage of predicted FEF25%-75%, adds little extra information to that obtained from a symptom history in assessing asthma severity," the researchers concluded. "FEV1/FVC, however, does appear to add value to this assessment, suggesting that this parameter should be used in determining asthma severity in adolescents." (van Dalen C, et al. Arch Pediatr Adolesc Med 2008;162:1169-1174.)

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