Digestive Symptoms in Healthy People and Subjects With Irritable Bowel Syndrome: Validation of Symptom Frequency Questionnaire

Abstract

Goals: The aim of this study was to validate the ability of symptom frequency questionnaire to differentiate between irritable bowel syndrome (IBS) patients and healthy subjects.

Background: A digestive symptom frequency questionnaire (DSFQ) was previously used in a food efficacy trial in a non-IBS population with mild gastrointestinal symptoms.

Study: We compared 2 well-defined populations: 100 IBS patients fulfilling Rome III criteria (mean age 32 y; range, 18 to 59 y), and 100 sex-matched and age-matched healthy subjects. Frequency of individual digestive symptoms (abdominal pain/discomfort, bloating, flatulence, borborygmi) was assessed using a 5-point Likert scale (from none to everyday of the week) and the IBS severity with the IBS-SSS questionnaire. Health-Related Quality of life (HRQoL) was assessed with the Food and Benefits Assessment (FBA) and Functional Digestive Disorders Quality of Life (FDDQL) questionnaires. The digestive (dis)comfort dimension of these questionnaires was considered as the main dimension for HRQoL.

Results: The DSFQ discriminated IBS from healthy subjects with a significant difference (P<0.001) between groups (estimated mean difference=5.58; 95% CI, 4.91-6.28). On the basis of the ROC curve (AUC=0.9479), a cutoff value of 5 gives a sensitivity of 92% and a specificity of 84%, with a positive likelihood ratio of 5.75. Composite score of symptoms correlated strongly (P<0.0001) with digestive discomfort measured by FDDQL (-0.816), digestive comfort measured by FBA (-0.789), and the IBS-SSS score (0.762).

Conclusions: Measurement of digestive symptom frequency by means of the DSFQ can differentiate IBS from healthy subjects, and shows a good correlation with other validated questionnaires (clinical trial #NCT01457378).

Conflict of interest statement

F.A. is a member of the scientific committee of Instituto Danone (Barcelona, Spain) and member of an advisory board for Danone Research (Paris, France). F.G. is a member of the scientific committee of Instituto Danone (Barcelona, Spain). D. Guyonnet and J.T. are employees of Danone Research. The remaining authors declare that they have nothing to disclose.

Figures

FIGURE 1

Receiver-operating curve (ROC) for distinguishing IBS (n=100) from HC (n=100) using composite score of digestive symptoms. Sensitivity versus 1−specificity is given for different cutoff values. The area under the curve was 0.95. HC indicates healthy control; IBS, irritable bowel syndrome.

FIGURE 2

Effect size of FBA questionnaire dimensions according to composite score of digestive symptoms (FAS population, n=200). Results are expressed as effect size for each class (2 to 5; 5 to 8; 8 to 16) for each dimension of the FBA questionnaire. The reference group used for effect size estimation is the group with the lowest composite score scores (0 to 2). Effect sizes of 0.5 and 0.8 are typically considered moderate and large between-group differences, respectively. FAS indicates Full Analysis Set; FBA, Food and Benefits Assessment.

FIGURE 3

Effect size of FDDQL questionnaire dimensions according to composite score of digestive symptoms (FAS population, n=200). Results are expressed as effect size for each class (2 to 5; 5 to 8; 8 to 16) for each dimension of the FBA questionnaire. The reference group used for effect size estimation is the group with the lowest composite score scores (0 to 2). Effect sizes of 0.5 and 0.8 are typically considered moderate and large between-group differences, respectively. FAS indicates Full Analysis Set; FBA, Food and Benefits Assessment; FDDQL, Functional Digestive Disorders Quality of Life.