This article, “COSMIN methodology for evaluating the content validity of patient-reported outcome measures: a Delphi study,” published in Quality of Life Research in 2018, presents a significant advancement in the assessment of Patient-Reported Outcome Measures (PROMs). Authored by C. B. Terwee, C. A. C. Prinsen, A. Chiarotto, M. J. Westerman, D. L. Patrick, J. Alonso, L. M. Bouter, H. C. W. de Vet, and L. B. Mokkink, the study addresses the critical challenge of evaluating content validity, which is considered the most important measurement property of a PROM.
The authors highlight that content validity refers to the degree to which an instrument’s content adequately reflects the construct it intends to measure, encompassing its relevance, comprehensiveness, and comprehensibility for the target population and context of use. A lack of content validity can detrimentally affect all other measurement properties, potentially leading to irrelevant items, missing concepts, decreased internal consistency, structural validity, interpretability, and even patient frustration or biased responses. The US Food and Drug Administration (FDA) and the COSMIN initiative both stress the importance of establishing content validity before evaluating other measurement properties.
Recognizing the difficulty in assessing content validity and the existing gaps in guidelines, this study pursued four key aims:
- To develop standards for evaluating the quality of PROM development.
- To update the original COSMIN standards for assessing the quality of content validity studies of PROMs.
- To develop criteria for what constitutes good content validity of PROMs.
- To develop a rating system for summarizing evidence on a PROM’s content validity and grading the quality of that evidence in systematic reviews of PROMs.
To achieve these aims, the researchers conducted an online 4-round Delphi study among a diverse international panel of 159 experts from 21 countries. Panelists rated their agreement with proposed standards, criteria, and rating issues on 5-point scales, providing arguments for their ratings. Consensus was defined as agreement from at least 67% of the panelists.
Key outcomes of this consensus-based study include:
- The establishment of new standards for evaluating the quality of PROM development (COSMIN box 1), covering both the identification of relevant items and the quality of cognitive interview studies.
- The update of COSMIN standards for evaluating the quality of content validity studies of existing PROMs (COSMIN box 2), with separate parts for patient and professional input.
- The definition of ten criteria for good content validity, focusing on item relevance for the construct, target population, and context of use, appropriateness of response options and recall period, comprehensiveness of key concepts, and comprehensibility of the PROM’s instructions, items, and response options.
- The development of a three-step rating system to evaluate PROM development and content validity studies against these criteria, determine an overall content validity rating for the PROM, and grade the quality of the evidence using a modified GRADE approach.
The resulting COSMIN methodology for content validity is more detailed, standardized, and transparent than previously published guidelines, including earlier COSMIN standards. This methodology is expected to contribute significantly to the selection and use of high-quality PROMs in both research and clinical practice, ultimately enhancing the reliability and validity of patient outcome assessments.
APA Reference:
Terwee, C. B., Prinsen, C. A. C., Chiarotto, A., Westerman, M. J., Patrick, D. L., Alonso, J., Bouter, L. M., de Vet, H. C. W., & Mokkink, L. B. (2018). COSMIN methodology for evaluating the content validity of patient-reported outcome measures: a Delphi study. Quality of Life Research, 27(5), 1159–1170. https://doi.org/10.1007/s11136-018-1829-0