The development and psychometric testing of an instrument to measure diabetes management self-efficacy in adolescents with type 1 diabetes.

Adherence to treatment is a major issue for people with diabetes mellitus, and attention has been given to improving self-management in persons with this chronic disease. Most studies show that knowledge alone will not improve self-management behavior. Self-efficacy, a concept introduced by Bandura, has been shown to be an important variable in improving health behaviors. In order to determine whether self-efficacy can influence self-management of diabetes, however, instruments to measure self-efficacy are needed in native languages at an appropriate developmental level, and with good psychometric properties. The study reported here was part of a larger project in the Netherlands, Belgium and the United States in which several instruments, measuring diabetes management self-efficacy, have been developed, both in English and Dutch, for different types of diabetes and different age groups. This article reports on the development and psychometric testing of an instrument measuring self-efficacy in adolescents with type 1 diabetes mellitus. Initially 30 items for the instrument were generated through focus group interviews and their relevance was judged by a team of 10 experts on self-management behavior in adolescents. The final instrument contained 26 items. The sample for psychometric testing consisted of 90 patients with type 1 diabetes who were between 12 and 18 years old. Cronbach's alpha of the instrument was 0.86. An exploratory factor analysis produced two factors which reflect general and more difficult diabetes self-management situations.