Validation of health-related quality of life instruments

The development of instruments to quantitate health-related quality of life (HRQOL) includes taking the appropriate and, in fact, essential steps to e nsure that the designated tool measures what it purports to measure and doe s it accurately and reliably. Such steps are not only critical in the devel opment of appropriate tools, but, when clearly presented, also serve to pro ve to the reader land reviewers) that the instrument is a legitimate one. K ey to the development of any HRQOL instrument are three fundamental concept s: validity, reliability, and responsiveness, Validity proves that the inst rument measures what it claims to measure. Reliability proves that the resu lts are reproducible in a stable setting, Responsiveness proves that the in strument is sensitive enough to record important differences or changes. Ea ch of these principles is discussed, including some examples of the applica tion of these principles in previously published HRQOL studies, The studies referenced are excellent examples of the methods used in the creation of a HRQOL scale, and the reader is strongly encouraged to review these in thei r entirety to fully grasp the concepts.