Health care has recently tended to take a more global perspective when
considering the individual patient. In addition to a measure of funct
ional status, the integration of the disease into the daily life of th
e individual, or his quality of life, is now being evaluated. This con
cept, while relatively recent, is the result, in part, of changes in a
ttitudes towards diagnosis and treatment of patients, particularly tho
se with chronic and severe diseases. Over time, what is sought is a me
asurement of change in the level of well-being during the evolution of
an illness. In clinical trials, the different levels that exist betwe
en 2 groups may be measured. The validation of a quality of life scale
requires both a qualitative and a quantitative approach with attentio
n being paid to the methodological issues in scale development. Specif
ic statistical techniques are used to modify evolving versions. The cr
oss-cultural adaptation of an existing scale into another language req
uires a rigorous qualitative phase before the quantitative phase is be
gun. The end product of this approach should be an equivalent scale, r
ather than a literal translation.