Cross-cultural validation of existing quality of life scales.

Health care 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 now being evaluated. This concept, while relatively recent, is the result, in part, of changes in attitudes towards diagnosis and treatment of patients, particularly those with chronic and severe diseases. Over time, what is sought is a measurement of change in the level of well-being during the evolution of an illness. In clinical trials, the different levels that exist between 2 groups may be measured. The validation of a quality of life scale requires both a qualitative and a quantitative approach with attention being paid to the methodological issues in scale development. Specific statistical techniques are used to modify evolving versions. The cross-cultural adaptation of an existing scale into another language requires a rigorous qualitative phase before the quantitative phase is begun. The end product of this approach should be an equivalent scale, rather than a literal translation.