Background: In a European trial in 8 countries, the subjective well-being of patients on alternative forms of treatment for insulin-dependent diabetes was compared using the 28-item WHO Well-Being Questionnaire, covering four dimensions of depression, anxiety, energy and positive well-being. The objective of the analysis reported here has been to identify the items of the WHO questionnaire which belong to an overall index of negative and positive well-being.
Methods: Adult patients at 10 study centres in 8 countries who had been on insulin for at least 2 years were invited to participate in a randomised, cross-over trial to compare insulin pump treatment with injection therapy. At each phase, patients completed questions on well-being and general health. Internal validity of the well-being index was evaluated by Cronbach's alpha and Loevinger's and Mokken's homogeneity coefficients, as well as factor analysis. External validity was evaluated by comparisons with results of the general assessment questions and by the ability to discriminate between the alternative forms of treatment.
Results: 358 patients had sufficient data for analysis. Ten items were found to constitute a valid index of well-being with respect to internal and external validity. Coefficients of homogeneity were acceptable and there was evidence for both concurrent and discriminant validity.
Conclusions: The WHO (Ten) well-being index includes negative and positive aspects of well-being in a single uni-dimensional scale. Its advantage lies in its ability to show overall change along the continuum of well-being, thus facilitating comparisons between patient groups and treatments. It is not specific to diabetes, and therefore may be useful as a disease-independent index of well-being in a broad range of health care studies.