MEASUREMENT OF FUNCTIONAL SEVERITY OF ASTHMA IN CHILDREN

The usefulness of surveys for measuring the severity of asthma in scho ol-age children depends on the availability of reliable and valid ques tionnaires. The aim of this study was to develop a measure of function al severity of asthma over the previous 12 mo, for use in population s tudies and in investigating treatment regimens. Of 10,198 children sur veyed, 9,192 (90%) in school Years 2, 7, and 10 (mean ages 8, 13, and 16 yr) in Melbourne were screened for wheeze. The parents of the 1,267 children with wheeze were interviewed. Symptoms and restriction of ac tivity due to asthma were analyzed using factor analysis and the parti al credit version of the item response theory measurement model. The r esult was a continuous severity scale that was highly consistent with the data, and with goodness of fit statistics indicating the severity of 97% of children was well described by the scale. The scale correlat ed significantly with school absence due to wheeze (r = 0.35), functio nal impairment during the 2 wk before interview (Functional Status II- R [FSII-R], r = 0.30), visits to medical care for wheeze (r = 0.22), a nd amount of medication (r = 0.36). For descriptive purposes, a simple index with four bands of severity was developed from the continuous s everity scale: low severity (47% of children with wheeze), moderate (3 0%), mild (18%), and high (5%). The scare and index facilitate standar dized description of the impact of asthma on daily life on the basis o f responses to six survey questions.