Psychometric properties of a questionnaire to measure adherence to treatment in patients with type 1 diabetes mellitus

Aim: To validate the psychometric properties of a questionnaire to measure adherence to treatment among people with type 1 diabetes mellitus and to evaluate its relationship with metabolic control. Design: A cross-sectional study of 167 adult people with type 1 diabetes mellitus recruited from the Endocrinology Service of University Hospital Doctor Peset (Spain). Methods: The validity of the content, construct and reliability of the instrument were evaluated and the results correlated with levels of glycosylated haemoglobin. Results: The questionnaire was composed of 25 items and 5 dimensions, with a score of 25-150 points and an internal consistency of 0.92, according to Cronbach's co-efficient a. The content of validity ratio and the construct (exploratory functional analysis, Kaiser-Meyer-Olkin index and Barlett's spherical test) were adequate. We observed a significant correlation between glycosylated haemoglobin levels and treatment adherence. Conclusion: The questionnaire to measure adherence to treatment in type 1 diabetes mellitus is consistent, reliable and valid, showing an excellent association with degree of metabolic control.