Assessing medication adherence among older persons in community settings

Background: Medication adherence is an important public health issue. To better understand its relevance among vulnerable populations requires the availability of a valid, reliable and practical measurement approach. Researchers have proposed various competing methods, including pill counts and self-report measures. Objective(s): To examine the utility of pill counts compared with self-report measures in the assessment of medication adherence among older home care clients. Method(s): The sample included 319 home care clients aged 65+ years randomly selected from urban and rural settings. During in-home assessments, nurses performed a medication review (including a pill count), administered the Morisky self-report scale, obtained supplemental information on medication use and completed the Resident Assessment Instrument for Home Care (RAI-HC). Responses to the Morisky scale and an open-ended question on nonadherence were combined to form a composite self-report measure of adherence. Result(s): Pill counts were either not feasible or considered inaccurate for 34.7% of subjects (47.5% of all eligible drugs). For the 205 subjects with available pill counts, estimates derived from the dispense date were found to underestimate adherence when compared with the actual start date reported by clients. The Morisky scale showed low reliability (Cronbach's alpha=0.42) and subjects' responses to the scale were often in disagreement with their responses to the open-ended question on nonadherence. There was poor agreement between the pill count and self-report measures. Conclusion(s): Our findings raise concerns about the feasibility and accuracy of pill counts as well as the validity of the Morisky self-report scale in the assessment of medication adherence among community-dwelling seniors. © 2005 Canadian Society for Clinical Pharmacology. All rights reserved.