Content Validity of a Questionnaire Based on the Theory of Planned Behavior to Assess the Psychosocial Determinants of Insulin Adherence

To verify the content validity of questions of an insulin adherence questionnaire based on the Theory Planned Behavior in outpatients with type 2 diabetes mellitus. The instrument was derived from a tool created to evaluate psychosocial determinants of adherence to oral antidiabetics medications in the Brazilian context, and was submitted for evaluation by a committee of experts and members of the target population. The item-level content validity index, the scale-level content validity index averaging calculation method, and the modified kappa coefficient were used to evaluate agreement among specialists. The comprehensibility of the instrument by members of the target population was qualitatively analyzed. The item-level content validity index was found to be lower than desired in 6 of the 20 items analyzed. Of these, one item was modified and 5 were excluded after the comprehensibility evaluation by members of the target population; one item from the perceived control scale was excluded. Content validation resulted in an instrument with 14 items, distributed in the domains intention (4 items), attitude (3 items), perceived norm (4 items), and perceived control (4 items) scales. The findings support good evidence of the content validity of the instrument for use among people with type 2 diabetes mellitus receiving insulin therapy. •Although adherence to drug treatment in type 2 diabetes mellitus reduces disease complications, nonadherence to insulin has been reported by outpatients.•The study provides a theory-based measure with content validity evidence, aimed at assessing the psychosocial determinants of adherence to insulin therapy behavior in people with type 2 diabetes mellitus.•Identifying the psychosocial determinants of insulin adherence therapy will enable health providers in delivering tailored theory-based interventions to promote insulin adherence.