BACKGROUND:

Asthma is both common and costly. Neither the risk factors of poor outcome nor the predictors of better outcome are 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 addressed a major research gap in secondary and tertiary prevention efforts.

DESIGN NARRATIVE:

A random sample of pulmonary and allergy subspecialists initially enrolled 600 persons with asthma identified in patient visit logs. This established panel completed 45 minute baseline and follow-up computer-assisted telephone interviews (CATI); 539 (90%) were successfully re-interviewed after 18 months of follow-up. A supplemental sampling frame of persons with asthma identified from family practitioners was completed as was a group with rhinitis but without asthma. Interviews assessed disease severity and other covariables using validated survey instruments. Pulmonary function and medical records were used to validate severity in a sub-sample of subjects. The study extended longitudinal follow-up study of this initial cohort.

Its analysis tested predictive models for the asthma outcomes of interest.