COSMIN reporting guideline for studies on measurement properties of patient-reported outcome measures

Purpose To develop a set of consensus and empirically based reporting recommendations for primary studies of the measurement properties of patient-reported outcome measures (PROMs). Methods This study included four phases: 1. Conducting an extensive literature review of recommendations for reporting of studies testing measurement properties of PROMs; 2. Preparing for the Delphi study by identifying experts; 3. Conducting three Delphi rounds aiming for consensus on the item list of recommendations found in phase 1; 4. Developing the COSMIN reporting guideline and user manual. Results The literature review resulted in 93 reporting items, included in the first Delphi round. A total of 84 individuals (from 12 countries) agreed to participate in the Delphi study, with 47, 30 and 25 responding in rounds one, two and three, respectively. After three rounds, we achieved consensus on a set of 71 items separated into a set of 35 "common" items (relevant to all studies on measurement properties) and 41 "specific" items (exclusively relevant to one of the nine measurement properties). Conclusion Consensus was achieved on a set of 71 items for inclusion in a reporting guideline for studies on measurement properties of PROMs. These items will guide researchers on the necessary information to include in their reports of investigations of measurement properties of PROMs. This guideline will likely improve the completeness of reporting of these important studies.