An Audit of Diabetes Dependent Quality of Life (ADDQoL) for Portugal: exploring validity and reliability

OBJECTIVE This paper describes the processes involved to ensure a diabetes-specific quality of life questionnaire [the "Audit of Diabetes Dependent Quality of Life" (ADDQoL)] retained the psychometric properties following cross-cultural adaptation from English to Portuguese. METHODS One hundred patients were recruited through community pharmacies located in Lisbon through a cross-sectional study design. Patients were asked to respond to the questionnaire on one occasion in time. Data were subjected to factor analysis, and internal consistency and discriminatory power analyses were undertaken. RESULTS In the Portuguese sample, 17 items loaded into one factor, with factor loadings above 0.43. The item "worries about the future" loaded weekly into this factor but if removed its internal consistency estimate increased very slightly (Cronbach's alpha=0.89 to 0.90). A greater negative impact of diabetes on 16 of the 18 quality of life domains was detected for insulin-treated patients, together with a greater negative impact on 14 of the 18 quality of life domains for patients with diabetic complications. The domain "freedom to eat" revealed the greatest negative impact in all patient subgroups, as described in its original version, so the psychometric properties were retained. Additionally, patients without diabetic complications reported a worse quality of life (greater negative impact) on the first overview item, present quality of life (Z=-2.25; p=0.024); whilst patients on insulin reported a greater negative impact of diabetes on their quality of life (Z=-1.94; p=0.053). CONCLUSION Generally, the Portuguese version for Portugal of the ADDQoL has shown to maintain its original psychometric properties, and could be recommended for use and further evaluation in subsequent studies.