Further testing of the reliability and validity of the ASK-20 adherence barrier questionnaire in a medical center outpatient population*

ABSTRACTObjective: This study examined the psychometric properties of the ASK-20 questionnaire, which was developed to assess barriers to medication adherence.Research design and methods: Patients with asthma, diabetes, and congestive heart failure were recruited from a university medical center. Participants in this convenience sample completed the ASK-20 questionnaire and other questionnaires. Approximately one-third of participants were randomized to a 2-week retest administration. Analyses examined the reliability and validity of the ASK-20.Results: A total of 112 patients participated (75.9% female; mean age = 46.7 years). The ASK-20 had good internal consistency reliability (Cronbach's alpha = 0.76) and test–retest reliability (0.80). Concurrent validity was demonstrated through significant correlations with the Morisky Medication Adherence Scale (r = −0.61, p < 0.001), condition-specific measures, and the SF-12 Mental Component Summary score (r = −0.40, p < 0.001). The correlation of the ASK-20 wit...