Psychometric Properties of the Persian Version of Brief Quality of Life Questionnaire in Bipolar Disorder

Objectives: To date, there is no specific scale to assess the quality of life in Bipolar Disorder (BD). The Quality of Life in Bipolar Disorder (QoL.BD) is the first questionnaire designed for this purpose. In this study, we aimed to examine the psychometric properties of the Persian Brief Quality of Life in Bipolar Disorder (Brief QoL.BD). Methods: After forward and backward translation of the questionnaire and comparing the two translations, the Persian version of the questionnaire was prepared to be tested. The statistical population comprised all patients and normal individuals in Tehran . The sample population included 118 patients with BD and 132 healthy individuals without the history of mental disorder; they were selected using a convenience sampling method. The study instruments included the Beck Depression Inventory-II, Bech–Rafaelsen Mania Rating Scale, the 36-Item Short-Form Health Survey (SF-36), and the Brief QoL.BD. Data were analyzed using SPSS and Lisrel statistical programs. Results: The confirmatory factor analysis indices indicated a relatively good model fit. Content validity estimates were also acceptable. Convergent validity was examined by calculating the correlation between the scores on the Brief QoL.BD and those on the SF-36 questionnaire; the results were found to be significant (r=0.36, P<0.01). Discriminant validity was assessed by comparing the Brief QoL.BD total scores between the groups of patients with BD and healthy individuals; the results indicated a significant difference between the two groups (t=65.09, P<0.01). The Cronbach’s alpha of 0.70 indicated an internal consistency. A test–retest reliability estimate of 0.89 indicated a high reliability of the scale. Discussion: The Brief QoL.BD has high validity and reliability in assessing the QoL of patients with BD in Iran.