Validation and psychometric properties of the self-efficacy for Appropriate Medication Use Scale in elderly Chinese patients

Background Self-efficacy for appropriate medication use is an important construct when evaluating the optimal use of medications. However, no instrument that assesses this construct in elderly Chinese patients has been shown to have valid psychometric properties. Objective To investigate the psychometric properties of the Chinese version of the self-efficacy for Appropriate Medication Use Scale in elderly patients with type 2 diabetes. Setting Geriatric patients were recruited from the endocrinology department of a tertiary hospital in Shanghai, China. Method Self-efficacy was assessed by the Chinese version of the Self-Efficacy for Appropriate Medication Use Scale in subjects who were at least 65 years old. Exploratory and confirmatory factor analyses were used to develop a psychometrically sound model of the scale. Main outcome measures Internal and test-retest reliability; convergent and discriminant validity of the scale; model fit indices of the factor model. Results The two-factor model of the self-efficacy for Appropriate Medication Use Scale was not suitable for elderly patients with respect to both item factor loadings and model fit indices. Conceptually overlapping scale items emerged when the scale was used in these patients. The final model developed appeared to achieve an ideal model fit and presented acceptable convergent and discriminant validity. Conclusions This study presented a Chinese version of the self-efficacy for Appropriate Medication Use Scale with psychometrically sound properties that will enable pharmacists, nurses and physicians to prospectively evaluate the impact of medication self-efficacy on a variety of health outcomes in elderly patients with type 2 diabetes.