Evaluation of methods used for estimating content validity.

The assessment of content validity is a critical and complex step in the development process of instruments which are frequently used to measure complex constructs in social and administrative pharmacy research. The aims of this study were to investigate the elements of content validity; to describe a practical approach for assessing content validity; and to discuss existing content validity indices. This is a narrative review of the assessment and quantification of content validity. It describes the key stages of conducting the content validation study and discusses the quantification and evaluation of the content validity estimates. Content validity provides evidence about the degree to which elements of an assessment instrument are relevant to and representative of the targeted construct for a particular assessment purpose. The assessment of content validity relies on using a panel of experts to evaluate instrument elements and rate them based on their relevance and representativeness to the content domain. It is a three-stage process that includes; the development stage, judgment and quantifying stage, and revising and reconstruction stage. To quantify the expert judgments, several indices have been discussed in this paper such as the content validity ratio (CVR), content validity index (CVI), modified-Kappa, and some agreement indices. A practical guide describes the process of content validity evaluation is provided. In summary, content validation processes and content validity indices are essential factors in the instrument development process, should be treated and reported as important as other types of construct validation. Determining item CVI and reporting an overall CVI are important components necessary to instruments especially when the instrument is used to measure health outcomes or to guide a clinical decision making. Content validity deserves a rigorous assessment process as the obtained information from this process are invaluable for the quality of the newly developed instrument.