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

• Published in: Current medical research and opinion 2008-11, Vol.24 (11), p.3197-3206
• Main Authors: Matza, Louis S., Yu-Isenberg, Kristina S., Coyne, Karin S., Park, Jinhee, Wakefield, Jessica, Skinner, Elizabeth P., Wolever, Ruth Quillian
• Format: Article
• Language: English
• Subjects: Academic Medical Centers; ASK; Asthma - diagnosis; Asthma - epidemiology; Asthma - therapy; Chronic diseases; Communication Barriers; Cross-Sectional Studies; Diabetes Mellitus, Type 2 - diagnosis; Diabetes Mellitus, Type 2 - epidemiology; Diabetes Mellitus, Type 2 - therapy; Female; Heart Failure - diagnosis; Heart Failure - epidemiology; Heart Failure - therapy; Humans; Male; Medication adherence; Medication Adherence - statistics & numerical data; Middle Aged; Outpatients - statistics & numerical data; Population; Quality of Life; Reliability; Reproducibility of Results; Surveys and Questionnaires - standards; Treatment adherence; Treatment persistence; Validity
• ISSN: 0300-7995; 1473-4877
• DOI: 10.1185/03007990802463642

ABSTRACT Objective: 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 with proportion of days covered by filled medication prescriptions in the past 6 months (based on pharmacy claims) was relatively weak (r = −0.13), but in the expected direction. The ASK-20 total score significantly discriminated among groups of patients who differed in self-reported indicators including the Morisky score; missing a medication dose in the past week; number of days medication was not taken as directed; and treatment satisfaction. Conclusion: The ASK-20 demonstrated adequate reliability and validity, and it may be a useful measure of barriers to treatment adherence across a spectrum of chronic diseases. Limitations related to scale construction, lack of longitudinal data, and item characteristics are discussed.