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 Table of Contents  
ORIGINAL RESEARCH REPORT
Year : 2021  |  Volume : 18  |  Issue : 1  |  Page : 42-51

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


1 Department of Practice of Medicine, Mahesh Bhattacharyya Homoeopathic Medical College and Hospital, Government of West Bengal, Kolkata, West Bengal, India
2 Department of Materia Medica, National Institute of Homoeopathy, Under Ministry of AYUSH, Government of India, Kolkata, West Bengal, India
3 Department of Organon of Medicine, State National Homoeopathic Medical College and Hospital, Govt. of Uttar Pradesh, Lucknow, Uttar Pradesh, India
4 Department of Repertory, D. N. De Homoeopathic Medical College and Hospital, Govt. of West Bengal, Kolkata, West Bengal, India

Date of Submission28-May-2020
Date of Acceptance11-Jul-2020
Date of Web Publication2-Feb-2021

Correspondence Address:
Dr. Mohan Giri
Department of Practice of Medicine, Mahesh Bhattacharyya Homoeopathic Medical College and Hospital, Government of West Bengal, Drainage Canal Road, Doomurjola, Howrah - 711 104, West Bengal
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jcls.jcls_44_20

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  Abstract 


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 α 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.

Keywords: Bengali language, confirmatory factor analysis, internal consistency, irritable bowel syndrome quality of life questionnaire, principal component analysis


How to cite this article:
Giri M, Roy S, Nahar L, Paul S, Chattopadhyay A, Ali SS, Basu A, Koley M, Saha S. Psychometric evaluation of the Bengali version of irritable bowel syndrome quality of life questionnaire: A cross-sectional study. J Clin Sci 2021;18:42-51

How to cite this URL:
Giri M, Roy S, Nahar L, Paul S, Chattopadhyay A, Ali SS, Basu A, Koley M, Saha S. Psychometric evaluation of the Bengali version of irritable bowel syndrome quality of life questionnaire: A cross-sectional study. J Clin Sci [serial online] 2021 [cited 2021 May 16];18:42-51. Available from: https://www.jcsjournal.org/text.asp?2021/18/1/42/308599




  Introduction Top


Irritable bowel syndrome (IBS) is a prevalent functional gastrointestinal disorder characterized by chronic abdominal pain or discomfort and altered bowel habits. The Rome IV criteria are frequently used for the clinical diagnosis and classification of IBS – IBS-C (predominant constipation), IBS-D (predominant diarrhea), IBS-M (both constipation and diarrhea), and IBS-U (unsubtyped).[1],[2] It is the most common gastrointestinal disorder of all age groups, which remains undiagnosed and/or until symptoms get severe, patients do not seek medical help. Thus, it has a significant disease burden in terms of increased absenteeism from school or work and reduced health-related quality of life (QOL).[3] The pooled regional prevalence rates are 17.5% in Latin America, 9.6% in Asia, 7.1% in North America, Europe, Australia, New Zealand, and 5.8% in the Middle East and Africa.[4] Shah et al.[5] reported a prevalence of 7.6% from Mumbai using Manning criteria; Ghoshal et al.[6] reported a prevalence of 4.2% in a prospective multi-center study using clinical criteria. Severe IBS can significantly reduce QOL, disrupt activities of daily life, and result in exorbitant health-care costs.[7] Patients have serious mental burdens such as anxiety, depression, embarrassment, dissatisfaction, frustration, stress, and self-consciousness. Patients conceal about their sufferings and seek least medical help due to the fear that their problem and impact on QOL will not be understood seriously by health professionals, and there will be a social stigma in the society.[8]

IBS-QOL questionnaire is a 34-item psychometrically sound instrument developed for measuring health-related QOL in 753 patients suffering from IBS-D in a clinic in the USA.[9],[10] The questionnaire consists of 34 items; each item is provided with five-point Likert type response scale: Not at all (1), slightly (2), moderately (3), quite a bit (4), and extremely (5). There are eight subscale scores – dysphoria (items1, 6, 7, 9, 10, 13, 16, and 30), interference with activity (items 3, 18, 19, 22, 27, 29, 31), body image (items 5, 21, 25, 26), health worry (items 4, 15, 32), food avoidance (items 11, 23, 28), social reaction (items 2, 14, 17, 34), sexual (items 12, 20), and social relationships (items 8, 24, 33). It was found to be a psychometrically valid measure and possessed the significant capability to detect the change by analysis of treatment effect. The initial version of the questionnaire was conceptualized by Patrick, et al.[11] and later further modified by Drossman, et al.[12] Drossman et al. established that a clinically meaningful improvement was defined by 14-point improvement in the IBSQOL questionnaire.[13]

Till date, there is no available Bengali version of the IBSQOL questionnaire. We intended to develop the Bengali version of the questionnaire (IBSQOL-B) through standardized forward-backward translation, and subsequently evaluating whether it was a psychometrically sound tool to measure the construct and to examine its cross-cultural adaptation considering linguistic equivalence.


  Patients and Methods Top


Study design

This noninterventional, cross-sectional, validation study was a mixed-method study; it consisted of standardized translation procedures, face validation by pilot testing, and field testing and psychometric assessment of the IBSQOL-B questionnaire.

Study setting

It was conducted at two sites– Medicine outpatient of Mahesh Bhattacharyya Homoeopathic Medical College and Hospital, Howrah, under Govt. of West Bengal, and Materia Medica outpatient of National Institute of Homoeopathy (NIH), Kolkata, under Ministry of AYUSH, Govt. of India; both institutions affiliated to The West Bengal University of Health Sciences, Kolkata, West Bengal. Institutional Ethics Committees (IECs) approved the protocol before initiation [Ref. No. 1919/MBHMCH/CH/PRIN/ADM/15, dated 26.15.2015 and 5-023/NIH/PG/Ethical Comm. 2009/Vol. III/1968(A/S); dated 27.03.2017. The conduct of the study was supervised by the IECs and was in compliance with the Declaration of Helsinki.

Questionnaire translation stages

  1. Forward translation: An expert committee was constructed, consisting of trained psychologists experienced in scale development and psychiatrist, gastroenterologists, linguistic experts, and research methodologists. First, two Bengali speakers, one psychologist, and one gastroenterologist translated the English version of the IBSQOL questionnaire into Bengali (T1 and T2)
  2. Synthesis of T1, 2: The two translators then agreed on a consensus version of the translation (T1, 2). Then the expert committee verified the version
  3. Back translation: Two English language translators (BT1 and BT2; one psychologist and one gastroenterologist), blinded to the original English version, translated T1, 2 back into English independently
  4. Committee review: All the translations (T1 and T2, T1, 2, B1, and B2) were reviewed by the committee, and a written report was prepared comparing the back-translations with the forward translations. Based on these, the prefinal version was developed
  5. Face validation: The prefinal version of the questionnaire was tested on randomly chosen ten patients visiting the outpatient clinics of the two hospitals for the purpose of testing contextual clarity, layout, language transparency, ease of understanding the content and use, comprehensibility of the instructions and response scales. Difficulties, if any, were noted. A written report was prepared by the interviewers, including detected insufficiencies and recommended changes and was then submitted back to the committee
  6. Committee appraisal: The final version of the IBQOL-B was developed by the committee based on the inputs from face validity (supplementary file). The different translation stages and the complete study flow are presented in [Figure 1]
  7. Field testing and validation: During the development of the original English version, the content validity of the IBSQOL-B questionnaire was already evaluated, and we refrained from repeating so [Figure 1].
Figure 1: Study flow diagram

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Inclusion criteria

Inclusion criteria were the patients suffering from IBS-D (ICD-10 diagnosis code K58.0) as per Rome III diagnostic criteria[2] and symptomatic for at least 2 days/week over 3 months, both sexes, age 18–65 years, literate patients with proficiency in reading Bengali, patients willing to participate in the study and giving written informed consent.

Exclusion criteria

Exclusion criteria were the patients who were too unwell to take part, diagnosed cases of unstable psychiatric complaints or other systemic diseases affecting QOL, any major gastro-intestinal surgery in the last 6 months, currently receiving standard or any other therapy for IBS and/or homeopathic treatment for any chronic condition(s), pregnant and lactating women, self-reported immune-compromised conditions, and substance abuse and/or dependence.

Sample size

Although recommendations for the adequate sample size to conduct factor analysis lack clear scientifically sound recommendations and remain controversial,[14] still a sample size between 50 and 250 is usually preferred, with most authors recommending at least 100 participants.[15] Participants to item ratio (5:1 or 10:1) is also used to calculate the sample size based on Gorsuch's formula,[16] thus necessitating 170–340 participants in this study. However, out of 382 participants approached, we were able to capture 350 responses in total with a response rate of 91.6%, of which the first 175 were subjected to principal component analysis (PCA) and the next 175 to confirmatory factor analysis (CFA).

Sampling

Patients suffering from IBS who attended the outpatients of the two hospitals on the days of data collection were approached by consecutive sampling and were invited to participate in the study subject to fulfillment of the prespecified eligibility criteria.

Data collection

Before obtaining responses on the IBSQOL-B, all the participants were provided with patient information sheets in local vernacular Bengali, and written informed consents were obtained. Patients' privacy was maintained by concealing all the identifiable information. Another section in the questionnaire sought information regarding patients' sociodemographic features. The filled-in questionnaires were put inside envelops and sealed at the study site. Thirty randomly chosen participants were selected for retest visits at approximately 2–3 weeks interval to fill the same questionnaire again. All the data were extracted in a specially designed Microsoft Excel spreadsheet and that was analyzed statistically.

Statistical analysis

It was conducted by using IBM® Statistical Package for Social Sciences® software, version 20.0 and SPSS Amos® version 20.0 (IBM Corp., Armonk, NY, USA). First, adequacy of the sample was checked using Kaiser–Meyer–Olkin (KMO) value and data appropriateness for PCA using Bartlett's test of sphericity. The KMO value 0.50 and above[17] with significant Bartlett's test of sphericity (P < 0.05) was considered appropriate for factor analysis. Then, exploratory factor analysis (EFA) using PCA with orthogonal rotation by varimax (eigenvalue above 1) was conducted to examine the unidimensionality of the construct. The purpose was to test how much the groups of items represent a common underlying (latent) variable. In this, a dataset is simplified by reducing data dimensionality by eliminating the components with small eigenvalues (explained variance per variable) and, therefore, of lesser significance. Only factors with loadings of 0.40 and above were retained. Weak loadings that is, failure to load > 0.39 on any component and general loadings of 0.40 on more than one component, would lead to the exclusion of the items from the matrix. Next, IBSQOL-B reliability was evaluated by analyses of internal inconsistency and test-retest reliability. High internal consistencies were denoted by Cronbach's alpha of 0.5–0.7[18] and average item-total correlation in a moderate range of 0.3–0.9. The alpha value of 0.9 and above was considered as excellent, while no meaningful construct was indicated by a correlation near 0.[19] Intra-class correlation coefficient (ICC) values above 0.7 indicated that IBSQOL-B was stable over time, 0.4–0.7 indicated fair reliability, while poor reliability was demonstrated by values < 0.4.[20] Paired t-tests were used on randomly chosen 30 patients' responses to evaluate whether the change in scores on the IBSQOL-B between the test-retest evaluations was statistically significant. Correlation statistics were used to assess the inter-item correlations between domains (item discriminant validity) and the overall IBSQOL-B (internal item convergence). The instrument was considered to be internally consistent if the correlation value was found to be 0.4 or higher. Finally, a CFA model was developed to verify the goodness-of-fit of the a priori detected scales as suggested by EFA. Actually, the objective of CFA is to explain as much of the variation as possible with the model specified and to test whether the data fit a hypothesized measurement model. CFA allows verifying the factor structure of a set of the observed variables by testing the hypothesis that a relationship exists between the observed variables and their underlying constructs. Thus, it is a multivariate analysis technique to analyze structural relationships. Causal modeling or path analysis hypothesizes causal relationships among both the manifest (observed directly and endogenous/dependent; presented in rectangular boxes) and latent variables (factors or hypothetical exogenous constructs that are presumed to exist, but not measured or observed directly and are invoked to explain observed covariations; presented in oval shapes) and tests the causal models with a linear equation system. In CFA, specific hypotheses are framed about the structure of factor loadings, and then the inter-correlations are tested. The goodness of fit of the CFA models was evaluated utilizing the following multiple fit indices: Comparative Fit Index (CFI), Normed Fit Index (NFI), Tucker Lewis Index (TLI), Root Mean Square Error of Approximation (RMSEA), Standardized Root Mean Square Residual (SRMR), Bayesian Information Criterion (BIC), and Hoelter index. The recommendations for cutoff values indicating a good model fit are CFI or TLI ≥0.95, RMSEA ≤0.6, and SRMR ≤0.8.[21],[22] Statistical tests were two-tailed and were conducted with α fixed at 0.05.


  Results Top


Descriptive statistics

Descriptive statistics, namely sociodemographic features and obtained response percentages on individual items on IBSQOL-B questionnaires, have been presented. IBQOL-B questionnaire responses were also presented in terms of means, standard deviations, medians, interquartile ranges, skewness, and kurtosis of each individual item [Table 1], [Table 2], [Table 3].
Table 1: Baseline sociodemographic features of the respondents (n=350)

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Table 2: Descriptive statistics of the irritable bowel syndrome quality of life -Bengali version responses (n=350)

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Table 3: Response percentages on irritable bowel syndrome quality of life -Bengali version questionnaire (n=350)

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Exploratory factor analysis

Sample size was adequate, as evidenced by the KMO = 0.928 (Chi-square: 4284.193, P < 0.001), much greater than the minimum Kaiser criterion of 0.5. A significant Bartlett's test of sphericity (df = 561, P < 0.001) also signified that the R-matrix was not an identity matrix. We performed extraction using the principal component method for determining how many factors best explained the observed covariation matrix within the data set. The screeplot revealed high eigenvalue for the first 6 components, and thereafter, the curve began to tail off gradually before the final plateau was reached [Figure 2]. The correlation matrix was searched for values > 0.9 to identify multi-co-linearity and singularity. Multi-colinearity was not a problem for the dataset. All the items correlated well, and none of the correlation coefficients were predominantly large; thus contradicting the elimination of any item at this stage. The sample size of 175 was adequate for running PCA as the average communalities after extraction was 0.671, above the preferred cutoff of 0.5. The factor component matrix also supported the scree plot by representing information from the initial unrotated solution and extracting six components explaining 67.1% of the total variance [Table 4]. Each of the components with their respective Eigenvalues and percentage of total variances explained are presented in [Table 4]. The values were weights that related the item (or variable) to the respective factor. The display of coefficients was sorted by size. Factor loadings were similar to regression weights (or slopes) and represented the strength of the association between the variables and the factors. The rotated (varimax) component matrix was a matrix of factor loadings for each variable onto each factor. The absolute values <0.4 were suppressed, ensuring that factor loadings within ±0.4 were not displayed in the output. After conducting factor rotation, those items were eliminated that loaded onto the same factor with lower loadings. Five sub-components and one ingle isolated item no. 5 of the main construct were identified and named as below [Table 5]:
Figure 2: Scree plot

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Table 4: Total variances explained (n=175; extraction by principal component analysis)

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Table 5: Rotated component matrix by varimax - factor loadings revealing 5 component structures and 1 individual isolated item (n=175)

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  1. Items 1, 4, 6, 7, 8, 9, 10, 15, 16, 18, 19, 30, 31: “Psychological impact”
  2. Items 11, 21, 22, 23, 24, 25, 27, 28, 29: “Limitation of daily activities”
  3. Items 2, 13, 26, 32, 33, 34: “Displeasure”
  4. Items 12, 14, 20: “Limitation of sexual activity”
  5. Items 3, 17: “Over concern”
  6. Item 5: “Flatulence.”


Item 5 remained isolated, did not load on any factor, and hence, it was not classifiable. Descriptive statistics of the identified components were presented in terms of means, standard deviations, medians, interquartile ranges, skewness, and kurtosis [Table 6].
Table 6: Descriptive statistics of the newly identified components of the irritable bowel syndrome quality of life -Bengali version questionnaire

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Internal consistency

The Cronbach's alpha value and ICC for the overall IBSQOL-B were 0.965 (95% confidence interval 0.960–0.970) and Guttman's split-half coefficient was 0.940, indicating reliability as excellent. The inter-component correlation matrix also substantiated the IBSQOL-B questionnaire as internally consistent or reliable [Table 7] and [Table 8].
Table 7: Internal consistency of the irritable bowel syndrome quality of life -Bengali version questionnaire overall and its components (n=350)

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Table 8: Inter-component correlation matrix (n=350)

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Test-retest reliability

On test-retest assessment, IBSQOL-B subscale scores and total scores were largely stable with insignificant mean differences (all P > 0.05), thus indicating acceptable test-retest reliability [Table 9].
Table 9: Test-retest reliability of the irritable bowel syndrome quality of life -Bengali version questionnaire components and overall score (n=30)

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Confirmatory factor analysis

The path coefficients of the CFA model are not correlation coefficients. The meaning of the path coefficient theta (for example, 0.72) is that if the domain “restraint” increases by one standard deviation from its mean, the domain “compulsion' would be expected to increase by 0.72 its own standard deviations from its own meanwhile holding all other relevant regional connections constant. The indices of CFA that confirmed model fit (Chi-square = 1238.436, degrees of freedom = 485, P < 0.001) were: CFI = 0.819, NFI = 0.736, TLI = 0.803, RMSEA = 0.094, SRMR = 0.130, BIC = 1630.960, and Hoelter index (at α 0.05) =76, indicating a satisfactory model fit [Figure 3].
Figure 3: The confirmatory factor analysis model

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  Discussion Top


IBSQOL is a validated questionnaire comprised of 34 questions and aimed at assessing QOL in IBS-D sufferers; but, until now, no validated Bengali version of the questionnaire was available. The English questionnaire underwent standardized forward-backward translation to produce the IBSQOL-B version. EFA using PCA of the IBSQOL-B identified five components and a single isolated item. The overall goodness of fit of the model was further confirmed by CFA. IBSQOL-B appeared to be valid and reliable with Cronbach's α, ICC coefficients, and test-retest reliability revealing as excellent.

One of the major strengths of this study was to apply EFA and CFA on two different samples of 175 patients suffering from IBS-D. Unlike other validation studies, there was no control (normal/healthy) group; hence, the assessment of item discriminant validity was not possible. Besides, the responsiveness of the questionnaire was not assessed because the treatment offered by the study sites was homeopathy exclusively, and that was not an accepted standard treatment for IBS-D until now. Our findings revealed that the internal consistency was excellent and comparable to the existing versions. However, a single individual component showed a fairly low Cronbach's alpha. Alpha measure depends on the number of items and covariances between items. A score <0.70 suggests that the items within the tool may not be measuring the same underlying construct, and poorly correlated items need to be deleted. However as the number of items was not too many, and the overall score was higher than 0.30, and retaining all the items revealed a satisfactory fit in the CFA model, we decided not to eliminate any of the items. It should also be kept in mind that alpha has very strict assumptions, including unidimensionality, uncorrelated errors, and identical covariances between the items (tau equivalence). In most of cases, these assumptions are violated, and thus, over-or underestimates true reliability. Thus alpha may not be the best choice for measuring reliability. The probable alternative may be Guttman's lambda or McDonald's omega, which are not based on tau-equivalence. There were satisfactorily high inter-component correlations among the subscales. While running PCA, the sample size achieved by us was satisfactory; and we achieved more than 175 samples to perform CFA. Forty-seven percent (16/34) of the items had strong factor loadings of 0.60 and above. Secondly, the IBSQOL-B was administered to the patients who were competent in reading and understanding the Bengali language. Therefore, the study findings are generalized to the Bengalee population only. Finally, the five components and an isolated single item model had an acceptable model fit in CFA. Thus, further translation and validation of the questionnaire are warranted into other Indian languages and on the larger sample for better and large-scale utilization in a multi-ethnic Indian population. Another drawback was the consecutive sampling used that might have introduced sampling bias into the study.

A systematic review identified that there were seven instruments available for measuring the IBS-specific HRQOL and that the IBSQOL is currently the best one to use.[23] Internal consistency, reliability, structural and criterion validity, and responsiveness– all were rated as fair; however, some conflicting evidence for the structural validity were identified. Therefore, it was recommended to elucidate the factor structure or dimensionality of the IBSQOL further. The Turkey and Persian versions of the IBSQOL questionnaire[24],[25] yielded Cronbach's alpha value of 0.97 and 0.93, respectively; quite similar to ours, but were conducted on 200 and 126 samples only, respectively. Both Turkey and Persian versions were found to be valid and reliable.

Thus the validated IBSQOL-B served as an important patient-administered outcome questionnaire to measure QOL in IBS-D sufferers. Future research should include the utilization of the IBSQOL-B as an outcome measure in clinical trials. Hence, the responsiveness and sensitivity to change of the IBSQOL-B to measure symptoms and treatment effects need to be determined in future investigations. Finally, to confirm that IBSQOL-B can measure the impact of clinical treatment, the final step in this development will be to define a minimally important difference of change, reflecting a clinically meaningful difference. The identified components may provide an evaluation of efficacy or effectiveness of any targeted interventions. The IBSQOL-B has already been used in a homeopathy clinical trial[26] and subsequently is being used in two more homeopathy trials (CTRI/2019/10/021632 and CTRI/2019/11/021916).


  Conclusion Top


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. However, to strengthen the validity of the IBSQOL-B, further analyses are recommended. No information on ethics, consent or Helsinki.

Acknowledgment

The authors appreciate the kind help received from Dr. Malay Mundle and Dr. Shubhamoy Ghosh, Research Methodologist, Dr. Atanu Dogra and Mr. Kaustabh Manna, Psychologists, Dr. Sudipta Ghosh and Dr. Ashokananda Konar, Gastroenterologists, Mr. Kohinoor Chakraborty, and Mr. Indrajit Mitra, Linguistic Experts for their services as expert panelists in the review committee. We are also grateful to the patients for their sincere participation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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