Validity and reliability of the 19-item Audit of Diabetes-Dependent Quality of Life (ADDQoL-19) questionnaire in Chinese patients with type 2 diabetes mellitus in primary care

Background This study aimed to determine the psychometric properties of the 19-item Audit of Diabetes-Dependent Quality of Life (ADDQoL-19) in Chinese patients with type 2 diabetes mellitus (T2DM) in primary care setting. Methods The ADDQoL-19 and SF-12v2 were administered to 386 Chinese patients with T2DM in public primary outpatient clinic in Hong Kong. Internal consistency reliability was determined by Cronbach's alpha, whereas construct validity was assessed by the Spearman's correlations between the scores of the ADDQoL-19 and SF-12v2. Independent t tests were used in known-group comparisons to identify the differences in the ADDQoL-19 scores between respondents with different duration of diabetes, treatment modalities, body mass index and glycemic control. Results The ADDQoL-19 had a moderate to weak correlation with SF-12v2 in convergent validity but with statistically significant results in known-group comparisons. Good internal consistency was generated with an acceptable value of 0.81, which was comparable to original English version. Construct validity was proven except the convergent validity is found to be weak with the generic SF-12v2, which was similar to the results in prior psychometric studies. Conclusions Despite weak convergent validity, the ADDQoL-19 was found to have a satisfactory psychometric property, especially known-group comparisons and internal consistency reliability in the primary care setting.