Classification of asthma severity in children: the contribution of pulmonary function testing.

BACKGROUND Despite increasing awareness of the National Asthma Education and Prevention Program guidelines, the relative contribution of symptom frequency or pulmonary function to the recommended asthma severity levels remains poorly understood. OBJECTIVE To determine whether adding lung function measurements to clinical history substantially changes the asthma severity classification, thereby influencing treatment decisions. DESIGN Baseline data were studied from children enrolled in 2 multicenter studies: phase 1 of the National Cooperative Inner-City Asthma Study (1992-1994) (cohort 1) and the Inner-City Asthma Study (1998-2001) (cohort 2). SETTING Fifteen (8 for cohort 1 and 7 for cohort 2) major metropolitan inner-city areas in the United States. PARTICIPANTS Inner-city children aged 8 through 11 years with asthma. MAIN OUTCOME MEASURES Proportion of children reclassified from less severe asthma categories based on symptom frequency into more severe categories because of lung function. RESULTS Of children with symptoms of mild intermittent asthma, 22.8% in cohort 1 and 27.7% in cohort 2 would be reclassified as having either moderate or severe persistent asthma. Of children with symptoms of mild persistent asthma, 31.2% in cohort 1 and 33.3% in cohort 2 would be similarly reclassified. CONCLUSIONS In 2 different studies of inner-city children with asthma, approximately one third of the participants were reclassified into higher National Asthma Education and Prevention Program asthma severity categories when pulmonary function was considered in addition to symptom frequency. This may have direct implications for the undertreatment of asthma.