To the Editor.
—Drs Gill and Feinstein1 suggest that studies measuring quality of life should provide an explicit conceptual framework for this measurement and should take the respondent's perspective into account. Both proposals seem constructive. However, these authors fail to apply the sound principles they advocate to their own measurement of the "quality of measurements." For instance, just as health status should not be equated with quality of life, the face validity of an instrument should not be confused with its overall quality. The disregard of psychometric properties2-4 in defining an instrument's quality is particularly worrisome, because an instrument that has excellent face validity can be worthless if it does not satisfy minimum standards of reliability, construct validity, or sensitivity to change.Consider the "quality" of a single-item instrument consisting of the time-honored question "how are you?" to which the response is left open-ended. To fulfill the criteria
Perneger TV, Hudelson PM. The Quality of Quality-of-Life Measurements. JAMA. 1995;273(11):843-844. doi:10.1001/jama.1995.03520350025014