[Evaluation of quality of life: construction of a scale]

Research in public health has recently tended to take a more global perspective when considering the individual patient. In addition to a measure of functional status, the integration of the disease into the daily life of the individual, or his quality of life is what is being evaluated. This concept, while relatively recent (10-15 yrs), is the result, in part, of changes in the diagnosis and treatment of patients, particularly those with chronic and severe diseases. In clinical trials, what is sought is a measurement of change in the level of well being during the evolution of an illness or of the different levels that exist between two groups. The validation of a scale of this type requires both a qualitative and a quantitative phase with attention being paid to the methodological issues in scale development Specific statistical techniques are used to modify evolving versions. The adaptation of an existing scale into another language requires a rigorous qualitative phase before the quantitative phase is begun.