Prosthodont [Editorial

Testing health status ("quality of life") questionnaires for asthma and COPD P.W. Jones Two papers in this issue of the Journal address the problem of testing versions of health status (or "quality of life") questionnaires after translation from their origi-nal English [1, 2]. Tests of the validity of health ques-tionnaires fall into four main areas: internal consistency; discriminative properties, i.e. the ability to distinguish dif-ferent levels of disease between patients; evaluative pro-perties, i.e. the ability to detect clinically meaningful changes in health; and predictive validity, i.e. the ability to predict future changes in health or healthcare needs. It is clear from this list that the process of validation is long and complex. Indeed, it is never-ending. Each new stud