Explanation & Elaboration document of the COSMIN Reporting Guideline 2.0 for studies on measurement properties of patient-reported outcome measures

Purpose: We aimed to develop an Explanation & Elaboration document to provide explanations, rationales, and good examples of reporting for each item in the COSMIN Reporting Guideline 2.0. Methods: The development of the Explanation & Elaboration document was conducted in four phases. In phase 1, experts on measurement properties were invited as writers to draft explanations and examples for each item. The original COSMIN Reporting Guideline items into 22 clusters, each containing two to six items, which were self-assigned by writers based on expertise. In phase 2, a draft of the Explanation & Elaboration document was created. For each item, an ‘Explanation’, ‘Essential elements’, and ‘Item examples’ were written. The draft was reviewed by a team of reviewers for grammar, conciseness, and consistency with other COSMIN tools. In phase 3, the Explanation & Elaboration document was extensively revised considering the newly created COSMIN reporting guidelines 2.0. In phase 4, the final version incorporated feedback from all writers and final approval. Results: Eighteen writers drafted the item explanations and provided examples of good reporting. The Explanation & Elaboration document contains explanations of the General and Specific items. We explain the reasons why reporting of the item is recommended and how to report the items with examples of good reporting. Conclusion: The Explanation & Elaboration document of the COSMIN Reporting Guideline 2.0 facilitates comprehensive reporting of studies on measurement properties of PROMs and should be used in conjunction with the COSMIN Reporting Guideline 2.0.