Abstract
BackgroundDiarrhea-predominant irritable bowel syndrome (IBS-d) significantly diminishes the health-related quality of life (HRQOL) of patients. Psychological and social impacts are common with many IBS-d patients reporting comorbid depression, anxiety, decreased intimacy, and lost working days. The Irritable Bowel Syndrome Quality of Life (IBS-QOL) questionnaire is a 34-item instrument developed and validated for measurement of HRQOL in non-subtyped IBS patients. The current paper assesses this previously-validated instrument employing data collected from 754 patients who participated in a randomized clinical trial of a novel treatment, eluxadoline, for IBS-d.MethodsPsychometric methods common to HRQOL research were employed to evaluate the IBS-QOL. Many of the historical analyses of the IBS-QOL validations were used. Other techniques that extended the original methods were applied where more appropriate for the current dataset. In IBS-d patients, we analyzed the items and substructure of the IBS-QOL via item reduction, factor structure, internal consistency, reproducibility, construct validity, and ability to detect change.ResultsThis study supports the IBS-QOL as a psychometrically valid measure. Factor analyses suggested that IBS-specific QOL as measured by the IBS-QOL is a unidimensional construct. Construct validity was further buttressed by significant correlations between IBS-QOL total scores and related measures of IBS-d severity including the historically-relevant Irritable Bowel Syndrome Adequate Relief (IBS-AR) item and the FDA’s Clinical Responder definition. The IBS-QOL also showed a significant ability to detect change as evidenced by analysis of treatment effects. A minority of the items, unrelated to the IBS-d, performed less well by the standards set by the original authors.ConclusionsWe established that the IBS-QOL total score is a psychometrically valid measure of HRQOL in IBS-d patients enrolled in this study. Our analyses suggest that the IBS-QOL items demonstrate very good construct validity and ability to detect changes due to treatment effects. Furthermore, our analyses suggest that the IBS-QOL items measure a univariate construct and we believe further modeling of the IBS-QOL from an item response theory (IRT) approach under both non-treatment and treatment conditions would greatly further our understanding as item-based methods could be used to develop a short form.
Highlights
Diarrhea-predominant irritable bowel syndrome (IBS-d) significantly diminishes the health-related quality of life (HRQOL) of patients
Much of the original development and validation work on the Irritable bowel syndrome (IBS)-QOL items were replicated in the current paper
Despite some indications of improvements that could be made, the current 34-item instrument does work in IBS-d patients; it performs well on the classical set of psychometric assessments and is demonstrated to be: Approximately unidimensional as evidenced by the high first eigenvalue extracted from the Exploratory Factor Analysis (EFA) model as well as the high Coefficient α value observed among the items; reliable as evidenced by the consistently high RΛ and RT values; and correlated with other measures of IBS-d symptoms and outcomes—both new, like the Food and Drug Administration (FDA) Clinical Responders, and old, i.e., Irritable Bowel Syndrome Adequate Relief (IBS-AR)
Summary
Diarrhea-predominant irritable bowel syndrome (IBS-d) significantly diminishes the health-related quality of life (HRQOL) of patients. The Irritable Bowel Syndrome Quality of Life (IBS-QOL) questionnaire is a 34-item instrument developed and validated for measurement of HRQOL in non-subtyped IBS patients. Irritable bowel syndrome (IBS) affects an estimated 10-15% of people in western cultures [1]. It is characterized by recurrent abdominal pain and diarrhea [2] and can negatively impact health-related quality of life (HRQOL). HRQOL instruments were included in the study as secondary outcomes By subjecting this larger data set to procedures outlined by previous publications [6,7] we plan to confirm the original psychometric validation analyses of the non-subtyped IBS-QOL. We hope to assess how the IBS-QOL performs in strictly IBS-d patients
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