Psychometric evaluation of the Bengali version of irritable bowel syndrome quality of life questionnaire: A cross-sectional study

Background: Irritable bowel syndrome (IBS) has a significant impact on the quality of life (QOL). IBSQOL questionnaire is a 34-item valid instrument aimed at measuring QOL in IBS-D (predominant diarrhea) patients. To date, no Bengali version of the questionnaire is available. We aimed to develop so and examine its cross-cultural adaptability considering linguistic equivalence. Methods: IBSQOL Bengali version (IBSQOL-B) was produced by forward-backward translations. A cross-sectional study was conducted through consecutive sampling at Mahesh Bhattacharyya Homoeopathic Medical College and Hospital, Howrah, and National Institute of Homoeopathy, Kolkata. A mixed method study was conducted involving 350 patients suffering from IBS-D. The study consisted of standardized translation of the IBSQOL questionnaire into Bengali, followed by formal validation. Psychometric analysis was run to examine its factor structure, validity, and reliability. Results: The overall internal consistency was excellent (Cronbach's alpha and intraclass correlation coefficient 0.965; 95% confidence interval 0.960-0.970). Test-retest reliability (P > 0.05) was satisfactory. The Kaiser-Meyer-Olkin (KMO = 0.928) and Bartlett's test of sphericity (Chi-square 4284.193, P < 0.001) both suggested sample adequacy. In factor analysis, all the items loaded above the prespecified value of 0.4 and identified five components (psychological impact, limitation of daily activities, displeasure, limitation of sexual activity, and over concern) and one single isolated item; explaining 67.1% of the variation. The goodness-of-fit in CFA model was acceptable (Chi-square: 1238.436, P < 0.001; Comparative Fit Index = 0.819, Tucker-Lewis Index = 0.803, Root Mean Square Error of Approximation = 0.094, and Standardized Root Mean Square Residual = 0.130). Conclusions: The developed IBSQOL-B contains 34 items that are constructed within 5-component and a single isolated item model. It is a reasonably valid and reliable tool, enabled to measure the impact of IBS-D in QOL in Bengalee patients.