Medication Adherence Measurement in Chronic Diseases: A State-of-the-Art Review of the Literature

Background/Objectives: One of the most important self-management behaviors is following agreed-upon treatment recommendations. In chronic disease, which affects over one-third of adults, a critical behavior is taking prescribed medication. However, approximately half of patients with chronic conditions fail to adhere to medication recommendations. Research into medication adherence is complicated by the diversity of measurement methods and definitions, resulting in inconsistent outcomes. Accurate measurement is essential for clinical decision making and identifying effective interventions. This state-of-the-art review aimed to map the current landscape of adherence measurement in chronic disease management and provide evidence-based recommendations for future research and practice. Methods: Using a state-of-the-art review approach, we examined objective and subjective adherence measures in studies where medication adherence was a primary outcome, published from August 2019 to July 2024. The frequencies of each method type were calculated. In studies using more than one method within a sample, adherence outcomes were compared to assess their comparability. Results: Of 1036 screened records, 314 met the inclusion criteria. Self-report questionnaires were most frequently used (72% of studies), followed by pharmacy refill measures (22%), electronic monitoring (2.5%), and biologic assays (1.3%). Subjective measures were more frequently used due to their convenience and lower cost but they reduce the level of precision. Objective measures offered greater precision but at a higher cost and logistical complexity. Conclusions: Our findings suggest a dominant reliance on subjective measures. Standardizing definitions, thresholds, and reporting, and adopting multimodal measurement strategies, will improve the validity, comparability, and clinical utility of adherence research.