Constructing arguments for the interpretation and use of patient-reported outcome measures in research: an application of modern validity theory.

The past 100 years have witnessed an evolution of the meaning of validity and validation within the fields of education and psychology. Validity was once viewed as a property of tests and scales, but is now viewed as the extent to which theory and evidence support proposed interpretations and uses of test scores. Uncertainty about what types of validity evidence were needed motivated the current "argument-based" approach, as reflected in the 2014 Standards for Educational and Psychological Testing. According to this approach, investigators should delineate the assumptions required in order for a proposed interpretation or use to be plausible and then seek evidence that supports or refutes those assumptions. Though validation practices within the field of patient-reported outcome measurement have implicitly included many elements of the argument-based approach, the approach has yet to be explicitly adopted. To facilitate adoption, this article proposes an initial set of assumptions that might be included in most arguments for research-related interpretations and uses of scores from patient-reported outcome measures. The article also includes brief descriptions of the types of evidence that would be best suited for evaluating each assumption. It is hoped that these generic assumptions will stimulate further discussion and debate among quality of life researchers regarding how best to adopt modern validity theory to patient-reported outcome measures.