Content validity--establishing and reporting the evidence in newly developed patient-reported outcomes (PRO) instruments for medical product evaluation: ISPOR PRO good research practices task force report: part 1--eliciting concepts for a new PRO instrument.

The importance of content validity in developing patient reported outcomes (PRO) instruments is stressed by both the US Food and Drug Administration and the European Medicines Agency. Content validity is the extent to which an instrument measures the important aspects of concepts that developers or users purport it to assess. A PRO instrument measures the concepts most significant and relevant to a patient's condition and its treatment. For PRO instruments, items and domains as reflected in the scores of an instrument should be important to the target population and comprehensive with respect to patient concerns. Documentation of target population input in item generation, as well as evaluation of patient understanding through cognitive interviewing, can provide the evidence for content validity. Developing content for, and assessing respondent understanding of, newly developed PRO instruments for medical product evaluation will be discussed in this two-part ISPOR PRO Good Research Practices Task Force Report. Topics include the methods for generating items, documenting item development, coding of qualitative data from item generation, cognitive interviewing, and tracking item development through the various stages of research and preparing this tracking for submission to regulatory agencies. Part 1 covers elicitation of key concepts using qualitative focus groups and/or interviews to inform content and structure of a new PRO instrument. Part 2 covers the instrument development process, the assessment of patient understanding of the draft instrument using cognitive interviews and steps for instrument revision. The two parts are meant to be read together. They are intended to offer suggestions for good practices in planning, executing, and documenting qualitative studies that are used to support the content validity of PRO instruments to be used in medical product evaluation.