Cultural Adaptation and Preliminary Validation of Adherence Questionnaires for Japanese Patients with Breast Cancer: A Pilot Study.

Purpose: This pilot study conducted a cultural adaptation and preliminary validation of the Beliefs about Medicines Questionnaire (BMQ) and the Medication Adherence Rating Scale (MARS) for Japanese patients with breast cancer. Patients and Methods: The grammatical accuracy of the Japanese translations of the BMQ and MARS, which are originally in English, was assessed by 10 physicians. A pilot survey was conducted with 50 patients with breast cancer in Japan who were starting adjuvant endocrine therapy. Internal consistency was examined using item-total and item-rest correlations and Cronbach's alpha. Items with low correlations were flagged for revision or removal. Oncology experts further reviewed problematic items for clinical relevance and cultural appropriateness. Results: Several items showed low relevance, particularly those that were inconsistent with the Japanese healthcare context. In the BMQ, Q6 ("This medicine is a mystery to me") and Q14 ("Natural remedies are safer than medicines") had low item-rest correlations (r = 0.079 and 0.075, respectively). In the MARS, four items (Q3-Q5 and Q9) were redundant. Conclusion: This pilot study demonstrated the significance of culturally adapting the BMQ and MARS. Revising or removing culturally incongruent items improved their relevance and reliability for Japanese patients with breast cancer.