Self-Report Adherence Measures in Chronic Illness Retest Reliability and Predictive Validity

Background: Patient self-report is a practical method for measuring adherence, but little is known about its optimal use. Objectives: To examine the retest reliability and predictive validity of 3 different types of self-report adherence measures among-patients with common chronic illnesses. Research Design: Correlation and regression analyses of data from an ongoing randomized controlled trial. Subjects: Patients (N = 415) aged >= 40 years recruited from a primary care network with arthritis, asthma, chronic lung disease. congestive heart failure, depression, and/or diabetes mellitus, plus impairment in : I basic activity and/or a score of :4 on the 10-item Center for Epidemiologic Studies Depression Scale. Measures: Self-report adherence (administered variously at baseline, 2, 4, and 6 weeks, and 6 months): number of pills taken/number of pills prescribed (PT/PP), using 1-7 days recall, and global reports of medication adherence and overall adherence tendencies. Six-month functional Outcomes: Health Assessment Questionnaire (HAQ) and Short Form-36 (SF-36). Results: Correlation coefficients among contemporaneously administered 1-7 days PT/PP measures were >= 0.78. Correlations among, PT/PP measures and global adherence measures, and among PT/PP measures at 2 and 4 weeks. ranged from 0.11 to 0.54. PT/PP measures using >= 3-4 days recall significantly predicted adjusted 6-month HAQ but not SF-36 score. Conclusions: Self-report PT/PP and general medication adherence measures tap different behavioral constructs. Self-reported PT/PP at a given point in time is not necessarily representative of medication adherence over time. Among chronically ill patients, >= 3-4 days recall of PT/PP yield adherence estimates, which are practically as reliable and valid as longer intervals and which predict Functional outcomes.