Validation of a specific quality of life questionnaire for functional digestive disorders

Abstract

Background: Dyspepsia and irritable bowel syndrome are suitable conditions for assessment of quality of life. Their similarities justify the elaboration of a single specific questionnaire for the two conditions.

Aims: To examine the process leading to the validation of the psychometric properties of the functional digestive disorders quality of life questionnaire (FDDQL).

Methods: Initially, the questionnaire was given to 154 patients, to assess its acceptability and reproducibility, analyse its content, and reduce the number of items. Its responsiveness was tested during two therapeutic trials which included 428 patients. The questionnaire has been translated into French, English, and German. The psychometric validation study was conducted in France, United Kingdom, and Germany by 187 practitioners. A total of 401 patients with dyspepsia or irritable bowel syndrome, defined by the Rome criteria, filled in the FDDQL and generic SF-36 questionnaires.

Results: The structure of the FDDQL scales was checked by factorial analysis. Its reliability was expressed by a Cronbach's alpha coefficient of 0.94. Assessment of its discriminant validity showed that the more severe the functional digestive disorders, the more impaired the quality of life (p<0.05). Concurrent validity was supported by the correlation found between the FDDQL and SF-36 questionnaire scales. The final version of the questionnaire contains 43 items belonging to eight domains.

Conclusions: The properties of the FDDQL questionnaire, available in French, English, and German, make it appropriate for use in clinical trials designed to evaluate its responsiveness to treatment among patients with dyspepsia and irritable bowel syndrome.

Figure 1

Stepwise procedure for the elaboration of the functional digestive disorders quality of life (FDDQL) questionnaire. FDD, functional digestive disorders; IBS, irritable bowel syndrome; QoL, quality of life.

Figure 2

Distribution among dyspeptic and irritable bowel syndrome patients of mean scores for the functional digestive disorders quality of life (FDDQL) questionnaire scales. Scores for each scale ranged from 0 (poor quality of life) to 100 (good quality of life). Differences between dyspeptic and irritable bowel syndrome patients were significant for the diet, discomfort, and stress scales (p<0.05, Mann-Whitney U test).

Figure 3

Distribution of mean scores for functional digestive disorders quality of life (FDDQL) questionnaire scales according to the number of symptoms. Each scale score and global score ranged from 0 (poor quality of life) to 100 (good quality of life). Intrascale differences were significant for all scales except those for coping with and control of disease and stress, according to the number of symptoms (p<0.05, Mann-Whitney U test). Differences between global scores, according to the number of symptoms were significant (p<0.001, Kruskal-Wallis test).

Figure 4

Distribution of mean scores for the SF-36 questionnaire among dyspeptic and irritable bowel syndrome patients versus controls. Scores for each scale ranged from 0 (poor quality of life) to 100 (good quality of life).