Quality of life assessment in therapeutic trials: rationale for and presentation of a more appropriate instrument

In therapeutic trials, quality of life studies are usually based on a health model which results in a restrictive view. Therefore, it is important to clearly define the concept of the quality of life, since ambiguous concepts can alter the results. The key to this problem is the clear distinction between the two components of the quality of life, ie subjective and objective. This latter component is the only one considered in the current medical approach. The use of the subjective quality of life introduces a number of methodological problems not found when the objective quality of life is assessed, and thus requires a specific model which can be derived from the model of life goals used by sociologists. This model is presented here and illustrated with some results obtained with a new questionnaire, the Subjective Quality of Life Profile (SQLP) questionnaire. We suggest that both subjective and objective quality of life studies should be considered in order to emphasize the humanistic approach to therapeutic indications.