Continued study of the psychometric properties of the McGill quality of life questionnaire

The McGill Quality of Life Questionnaire (MQOL) is a widely used tool that has been specifically developed to measure the quality of life of patients facing a life-threatening illness. Preferably, a self-report instrument has an equal number of items worded positively and negatively. However, all the psychological scales of the MQOL are worded so that a high score is negative, whereas the existential scales are worded so that a high score is positive. The goal of this study was to investigate the influence of MQOL item formatting on patient responses. In order to do so, a modified version of the questionnaire was distributed to and completed by 205 patients in two oncology clinics. The modified version had an equal amount of items worded in a positive direction and negative direction in each of the domains. Results of this study were found to be different from those of other studies: the loading of the items was partly based on scale direction. These changes support the idea that the MQOL formatting has some impact on patient responses. However, factors were also determined by content. Given that MQOL has been widely used and the original formatting provides conceptually clearer subscales, we suggest maintaining the original format, keeping in mind the effect of formatting when interpreting scores.