Background: Current adherence scales often fail to assess the full spectrum of behaviors associated with safe and appropriate drug use and may be unsuitable for patients with limited health literacy. We sought to develop and evaluate a comprehensive yet brief Measure of Drug Self-Management (MeDS) for use in research and clinical settings among diverse patient groups.
Methods: Expert opinion, literature reviews, and interviews with patients and providers were utilized to create and revise potential items. Item performance testing was then conducted among 193 adult English-speaking patients with hypertension and diabetes. Factor analysis was used to inform item selection. Reliability was assessed via calculations of internal consistency. To assess construct and predictive validity, MeDS scores were compared with scores from the 8-item Morisky Medication Adherence Scale and relevant clinical measures (HbA1c, blood pressure, and low-density lipoprotein cholesterol).
Results: The MeDS demonstrated adequate internal consistency with a Cronbach's α of 0.72. The MeDS was significantly correlated with the Morisky Medication Adherence Scale (r= -0.62; P<0.001). The MeDS was also associated with clinical measures, with statistically significant correlations found between MeDS scores and low-density lipoprotein cholesterol (r= -0.27, P≤0.001) and diastolic blood pressure (r= -0.18, P=0.01).
Conclusion: The MeDS seems to be a valid and reliable tool that can be used to assess medication self-management skills among diverse patients, including those with limited literacy skills. Future studies are needed to test the tool in actual use and explore clinical applications.
Keywords: health literacy; measurement; medication adherence.