Use of changes in symptoms to predict changes in lung function in assessing the response to asthma therapy

The majority of adult patients with asthma are managed by primary care providers. Although there is no generally accepted gold standard for the assessment of asthma severity in general practice, treatment decisions and modifications to therapy are strongly influenced by patients' symptoms and history of asthma medication use.

The primary goal of this study was to determine whether there is a correlation between changes in asthma symptoms during treatment and changes in lung function, as measured by peak expiratory flow (PEF). A secondary goal was to compare the relative efficacy (in terms of improvement in asthma symptoms and lung function) of 3 commonly used asthma treatments: inhaled fluticasone propionate, inhaled salmeterol xinafoate, and oral zafirlukast.

This was a retrospective comparison employing regression analyses of asthma symptom and lung function data from 2890 male and female adolescent and adult patients with persistent asthma who were enrolled in 8 randomized, double-blind, double-dummy, parallel-group studies. Data on patients' self-rated symptoms, PEF, supplemental albuterol use, nighttime awakenings, and frequency of asthma exacerbations were used to ascertain whether there was a correlation between changes in asthma symptoms and changes in pulmonary function, and to compare treatment effects.

Changes in patients' ratings of asthma symptoms after treatment with study medications showed a strong correlation with changes in lung function. Similarly, changes in lung function were strongly correlated with changes in supplemental beta-agonist use and quality of life. In addition, fluticasone or salmeterol treatment resulted in significantly greater increases in mean morning PEF (P < 0.001), significantly greater decreases in symptom scores (P < or = 0.004), significantly fewer nights with awakenings due to symptoms (P < or = 0.017), and significantly greater reductions in supplemental beta-agonist use (P < 0.001) compared with zafirlukast treatment or placebo. Patients treated with fluticasone or salmeterol also experienced significantly lower rates of asthma exacerbation (3%) during treatment than did those receiving zafirlukast (7%) or placebo (12%) (P < 0.001 and P = 0.015, fluticasone and salmeterol, respectively).

These findings support the validity of primary care practitioners' basing asthma-management decisions on patients' symptoms.