Development and validation of a quality of life questionnaire for patients with colostomy or ileostomy

Abstract

Background: Quality of life of stoma patients is increasingly being addressed in clinical trials. However, the instruments used in the majority of these studies have not been validated specifically for stoma patients. The aim of this paper is to describe the development and validation of a quality-of-life instrument, "Stoma-QOL", specifically for patients with colostomy or ileostomy.

Methods: Potential items were formulated in English on the basis of the results of a series of semi-structured interviews with 169 adult stoma patients. The process resulted in a preliminary 37-item version, which was translated into French, German, Spanish and Danish, and administered repeatedly to 182 patients with colostomy or ileostomy. A psychometric selection of items was performed through Rasch Analysis. The measurement properties of the final questionnaire version were subsequently tested.

Results: The 20 items in the final questionnaire covered four domains--sleep, sexual activity, relations to family and close friends, and social relations to other than family and close friends. These items were found to define a unidimensional variable according to Rasch specifications (Infit MNSQ < 1.3). Internal consistency reliability calculated as Cronbach's alpha was 0.92, i.e., highly reliable. Spearman's correlation coefficients of scores across times of administration was > 0.88 (p < 0.01), indicating a high test-retest reliability. Item calibrations by country calculated as ICC were 0.81 (0.67-0.91 95% CI), confirming cross-cultural comparability across the European countries included in the study.

Conclusion: Given the adequacy of the metric properties of the Stoma-QOL suggested by the psychometric analyses, this study confirms the suitability of the instrument in clinical practice and in clinical research.

Figures

Figure 1

Development of the Stoma-QOL questionnaire.

Figure 2

Stoma-QOL Item Calibration of the items located within the spread of the person measures. (logit scores, the measurement unit common to both patients and items, are displayed down the middle of the map; patient, represented by a single dot, are arranged within the scale from better (top) to worse (down) quality of life; items are identified by the item number)