Study objective: To develop and evaluate a brief, easy-to-administer symptom assessment scale for use as a preference-based outcome measure in clinical trials and cost-effectiveness studies in asthma.
Design: Cross-sectional survey with 2-week reproducibility assessment.
Setting: Ambulatory care: university asthma and allergy center.
Participants: One hundred sixty-one adults with asthma, 59% female, mean age 35 ± 11 years. Mean FEV1 percent predicted was 86 ± 17%.
Interventions: The 11-item Asthma Symptom Utility Index (ASUI).
Measurements and results: Mean ASUI score for this sample was 0.71 ± 0.23, with a range from 0.02 to 1.0. The ASUI was reproducible (intraclass correlation coefficient = 0.74) and able to distinguish patients known to differ on disease severity according to clinician ratings (p < 0.001) and by an asthma disease severity scale score (p < 0.001). The instrument was also significantly correlated with FEV1 percent predicted (r = 0.27, p < 0.001), the Asthma Quality of Life Questionnaire (r = 0.77, p < 0.001), and the Health Utilities Index Mark 2 (r = 0.36, p < 0.001).
Conclusion: The results of this study support the reliability and validity of the ASUI, suggesting it will be a useful, complementary patient outcome measure for clinical trials and cost-effectiveness studies comparing treatment alternatives for persons with asthma.