Psychometric properties of the Norwegian version of the Audit of Diabetes-Dependent Quality of Life

Abstract

To examine the psychometric properties of the Norwegian version of the Audit of Diabetes-Dependent Quality of Life version 18 (ADDQoL-18). We assessed the reliability (Cronbach's alpha and intraclass correlations) and construct validity (confirmatory factor analysis and Pearson's correlation coefficients) of the instrument in a sample of 292 adults in Norway aged 42.3 (SD 14.2) years. Internal consistency (Cronbach's alpha 0.88) and 4-week test-retest stability (intraclass correlations=0.87) were satisfactory. Confirmatory factor analysis indicated that the one-factor structure of the ADDQoL-18 fits moderately (χ (2)/df ratio=3.846, comparative fit index=0.792, root mean square error of approximation=0.099). Standardized coefficients showed that all domains loaded >0.4, except for one item. We found a satisfactory correlation between the ADDQoL-18 and the SF-36 Health Survey summary scales (physical health and mental health summary scales) and the Hospital Anxiety and Depression Scale. The total score was negatively associated with HbA1c (r=-0.18; P<0.002), indicating that lower scores on the ADDQoL-18 were related to poorer glycemic control. Analysis regarding discriminant validity showed that the average weighted impact scores were mostly reduced among those reporting neuropathy and foot problems. The Norwegian version of the ADDQoL-18 showed high internal consistency, good test-retest reliability, and similar construct validity as the original instrument. Overall, the results supported the ADDQoL-18 being feasible for use in Norway.