Barriers to medication adherence in sickle cell disease: A comprehensive theory-based evaluation using the COM-B model.

BACKGROUND: Sickle cell disease (SCD) affects more than 100,000 Americans, with complications such as pain episodes and acute chest syndrome. Despite the efficacy of hydroxyurea in reducing these complications, adherence remains low. Study objectives were to examine barriers to hydroxyurea adherence, and to evaluate the relationship between barriers and their impact on adherence. METHODS: In this cross-sectional study, patients with SCD and their caregivers were enrolled if they were taking hydroxyurea. Study measures included demographics, self-report of adherence using visual analog scale (VAS), and the Disease Management and Barriers Interview (DMI)-SCD. The DMI-SCD was mapped to the Capability, Opportunity, Motivation, and Behavior (COM-B) model. RESULTS: Forty-eight caregivers (females 83%, median age 38 [34-43]) and 19 patients (male 53%, median age 15 [13.5-18]) participated. Using VAS, many patients (63%) reported low hydroxyurea adherence, while most caregivers (75%) reported high adherence. Caregivers endorsed barriers across multiple COM-B components, with physical opportunity (e.g., cost) and reflective motivation (e.g., SCD perceptions) being the most identified categories (48% and 42%), respectively. Patients' most identified barriers included psychological capability (e.g., forgetfulness) and reflective motivation (84% and 68%), respectively. Patients' and caregivers' VAS scores negatively correlated with the number of barriers (rs  = -.53, p = .01; rs  = -.28, p = .05) and COM-B categories (rs  = -.51, p = .02; rs  = -.35, p = .01), respectively, suggesting lower adherence with more endorsed barriers. CONCLUSIONS: Fewer barriers to hydroxyurea adherence were associated with higher adherence. Understanding barriers to adherence is essential to develop tailored interventions aimed at improving adherence.