Use of Existing Patient-Reported Outcome (PRO) Instruments and Their Modification: The ISPOR Good Research Practices for Evaluating and Documenting Content Validity for the Use of Existing Instruments and Their Modification PRO Task Force Report
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Abstract
Patient-reported outcome (PRO) instruments are used to evaluate the effect of medical
products on how patients feel or function. This article presents the results of an
ISPOR task force convened to address good clinical research practices for the use
of existing or modified PRO instruments to support medical product labeling claims.
The focus of the article is on content validity, with specific reference to existing
or modified PRO instruments, because of the importance of content validity in selecting
or modifying an existing PRO instrument and the lack of consensus in the research
community regarding best practices for establishing and documenting this measurement
property.
Topics addressed in the article include: definition and general description of content
validity; PRO concept identification as the important first step in establishing content
validity; instrument identification and the initial review process; key issues in
qualitative methodology; and potential threats to content validity, with three case
examples used to illustrate types of threats and how they might be resolved. A table
of steps used to identify and evaluate an existing PRO instrument is provided, and
figures are used to illustrate the meaning of content validity in relationship to
instrument development and evaluation. RESULTS & RECOMMENDATIONS: Four important threats
to content validity are identified: unclear conceptual match between the PRO instrument
and the intended claim, lack of direct patient input into PRO item content from the
target population in which the claim is desired, no evidence that the most relevant
and important item content is contained in the instrument, and lack of documentation
to support modifications to the PRO instrument. In some cases, careful review of the
threats to content validity in a specific application may be reduced through additional
well documented qualitative studies that specifically address the issue of concern.
Published evidence of the content validity of a PRO instrument for an intended application
is often limited. Such evidence is, however, important to evaluating the adequacy
of a PRO instrument for the intended application. This article provides an overview
of key issues involved in assessing and documenting content validity as it relates
to using existing instruments in the drug approval process.