Aim: To validate the Italian version of the World Health Organization (WHO)-Well-Being Questionnaire (WBQ) and the WHO-Diabetes Treatment Satisfaction Questionnaire (DTSQ) in Type 1 and Type 2 diabetic patients.
Methods: The cultural adaptation of the questionnaires was performed by using standard forward/backward techniques. Internal consistency reliability was estimated by Cronbach's alpha coefficient. Construct validity was evaluated using the Short Form-36 (SF-36) Health Status Questionnaire. Finally, the discriminative properties of the questionnaires were evaluated relative to the patients' characteristics. The questionnaires were administered to a random sample of patients identified in twelve outpatient diabetes clinics.
Results: Overall, 412 subjects were recruited, of whom 96 (23%) with Type 1 diabetes. Item-scale correlations were >0.40 for all the items. Cronbach's alpha coefficient was 0.86 for the WHO-DTSQ and ranged between 0.79 and 0.91 for the WHO-WBQ. High correlations were found between WHO-WBQ scales and the mental dimensions of the Short Form-36 (SF-36) questionnaire, but not between WHO-DTSQ and SF-36 scores. Women, obese subjects, those with longer diabetes duration and multiple complications showed a worse quality of life in all of the four areas of the WHO-WBQ. In Type 2 diabetic subjects, SF-36 scores, but not WHO-WBQ scores, were able to discriminate the population according to the treatment modalities. Lower levels of treatment satisfaction were related to female gender, longer diabetes duration, insulin treatment, presence of diabetes complications and HbA1c levels >7.0%. The flexibility of the treatement was perceived as a major problem even among patients treated with oral agents.
Conclusions: The WHO-DTSQ can be considered as a valuable instrument to be used internationally for the description of diabetes treatment satisfaction. The WHO-WBQ also shows adequate psychometric properties, but additional data are needed to clarify whether it is more sensitive than SF-36, the most widely used generic instrument.