This question implies a simple “yes” or “no” answer. There are some questions that can be answered appropriately with a positive or negative response. Do you have disability insurance? Have you ever had surgery? Are you pregnant? . . . The validity of an outcomes instrument, however, is not at all like being pregnant. An instrument can never be said to be “valid” in any unqualified sense. One might expect that an expertly developed fourth grade math test would be valid for discriminating math proficiency levels among fourth graders. Validity, however, is not portable. A test that is valid in a particular population for a particular purpose may not be valid for use in other populations and for other purposes. The hypothetical math test described above would not be a valid test of math proficiency of high school students nor would it be a valid test of the writing skills of fourth graders. Validation is an ongoing and never completed exploration and documentation of how a measure functions. The strength of the validity evidence is judged in the courtroom of scientific opinion. In fact, the judicial system provides a serviceable metaphor. Validation is the process of building a case for a measure. Various psychometric studies are undertaken and their results serve as “character witnesses” that reveal the level and nature of a measures’ usefulness in different populations and for different purposes.

To reiterate, the validation of an instrument is an ongoing process that is never completed. However, substantial qualitative and quantitative evidence has been gathered supports the validity of the PROMIS instruments. Below we describe some of this evidence. We believe that validity starts at the beginning. We share the view that “content validity is built into a test from the outset through the choice of appropriate items” [Anastasi A, 1988, Psychological Testing, New York, Macmillan Publishing Company, p. 122-127.]) The content-related validity of PROMIS instruments began in our use of patient interviews and review by expert review panels. Details about these activities can be found in DeWalt, D., Rothrock, N., Yount, S., Stone, A. A., & on behalf of the PROMIS cooperative group. (2007). Evaluation of item candidates: the PROMIS qualitative item review. Medical Care, 45(5), S12-21. Additional information about the validity of PROMIS instruments can be found in a triplet of articles published in the Journal of Clinical Epidemiology:

1. Cella, D., Riley, W., Stone, A., Rothrock, N., Reeve, B., Yount, S., Amtmann, D., Bode, R., Buysse, D. J., Choi, S. W., Cook, K. F., DeVellis, R., DeWalt, D., Fries, J. F., Gershon, R., Hahn, E., Pilkonis, P., Revicki, D., Rose, M., Weinfurt, K., & Hays, R. D. on behalf of the PROMIS Cooperative Group. (2010). Initial item banks and first wave testing of the Patient-Reported Outcomes Measurement Information System (PROMIS) network: 2005-2008. Journal of Clinical Epidemiology, 63(11) 1179-94

3. Rothrock, N. E., Hays, R. D., Spritzer, K., Yount, S. E., Riley, W., and Cella, D. (2010). Relative to the general US population, chronic diseases are associated with poorer health-related quality of life as measured by the Patient-Reported Outcomes Measurement Information System (PROMIS). Journal of Clinical Epidemiology, 63(11), 1195-1204.