Quality of life in Iranian patients with bipolar disorder: a psychometric study of the Persian Brief Quality of Life in Bipolar Disorder (QoL.BD)

Abstract

Purpose: To assess the reliability, validity, and factor structure of the Persian Brief Quality of Life in Bipolar Disorder (QoL.BD) in Iranian patients with bipolar disorder (BD).

Methods: After translation and cross-cultural adaptation of the Brief QoL.BD, we administered the questionnaire to 184 patients diagnosed with BD. To determine factor structure, we performed both exploratory and confirmatory factor analyses. To investigate the reliability, we assessed internal consistency, reproducibility and agreement. Construct validity was assessed by calculating correlations between the Brief QoL.BD and the Short Form-36 (SF-36), Positive And Negative Affect Schedule (PANAS), Hamilton Depression Rating Scale, Young Mania Rating Scale (YMRS) and Quality of Life Enjoyment and Satisfaction Questionnaire Short Form (Q-LES-Q-SF). We also investigated gender differences in interpretations of QoL.BD items.

Results: The results obtained from reliability analysis confirmed internal consistency (Cronbach's alpha was 0.87 and 0.89 for two assessments) and reproducibility and agreement (the intraclass correlation coefficient ranged between 0.74 and 0.94). Validity analyses showed that the items loaded on a single-factor structure. The inter-item correlations varied from 0.31 to 0.68. Significantly lower scores on the Brief QoL.BD were observed in people diagnosed with BD I compared to BD II. Significant correlations were observed between the Brief QoL.BD and SF-36 summary measures, HAMD, YMRS, Q-LES-Q-SF and PANAS subscales. Items in the Brief QoL.BD were interpreted similarly by men and women.

Conclusions: The Brief Persian QoL.BD is a psychometrically sound measure with acceptable validity and reliability and provides a rapid assessment tool for measuring QoL in patients with BD.

Keywords: Bipolar disorder; Factor analysis; Persian; Quality of life; Reliability; Validity.