Compliance from self-reported versus pharmacy claims data with metered-dose inhalers

OBJECTIVE: To determine how well self-reported compliance with metered-dose inhalers (MDIs) agrees with compliance determined from pharmacy claims data. Additional analyses were conducted to establish psychometric properties of the questionnaire. METHODS: A cross-sectional survey was performed of all adult enrollees with asthma of a managed care organization. The overall return rate was 63.4% (696/1098). Patients with persistent asthma and at least one prescription claim for a controller MDI during the four months preceding the survey were included. Pharmacy claims data were used to calculate a compliance ratio. Self-reported compliance was based on a four-item questionnaire. The primary end points were the percent-agreement and the overall correlation between the two measures. The questionnaire's internal reliability and construct validity were assessed using Cronbach's α and Pearson's correlations, respectively. Mean item response scores for compliant patients were compared with scores of noncompliant patients using the Student's t-test. RESULTS: One hundred questionnaire respondents met the study criteria. The mean ± SD compliance ratio was 0.52 ± 0.27, the mean ± SD self-reported compliance score was 4.07 ± 1.0. The overall percent agreement and correlation between self-reported compliance score and the compliance ratio were 75.5% and r = 0.348 (p = 0.01), respectively. The percent agreement was highest (85%) when noncompliant patients (by compliance ratio