The aim of this study is to assess the separate and interactive effects of asthma severity, subspecialty practice variation, asthma-related psychosocial variables, and other factors on asthma outcomes, including asthma-specific quality of life and activity limitations, health care utilization for asthma, and direct and indirect costs of asthma. Asthma is both common and costly. Neither the risk factors of poor outcome nor the predictors of better outcome are not well understood. Illness severity is clearly an important predictive factor in asthma, but may explain less variability in outcome than other determinants, such as patient-perceived asthma control, other asthma-related psychosocial measures, and the kind and extent of subspecialty care for asthma. By quantifying predictors of asthma-specific quality of life, functional status, services utilization, and the direct and indirect illness costs of asthma, this study addresses a major research gap in secondary and tertiary prevention efforts. A random sample of pulmonary and allergy subspecialists initially enrolled 600 persons with asthma identified in patient visit logs. This established panel has completed 45 minute baseline and follow-up computer-assisted telephone interviews (CATI); 539 (90%) have been successfully re-interviewed after 18 months of follow-up. A supplemental sampling frame of persons with asthma identified from family practitioners is in progress (target baseline n=180) and an additional referent group (n=200) with rhinitis, but without asthma is planned. Interviews will assess disease severity and other covariables using validated survey instruments. Pulmonary function and medical records will be used to validate severity in a sub-sample of subjects. The proposed study extends longitudinal follow-up study of this cohort. Its analysis will test predictive models for the asthma outcomes of interest.
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