Development of core outcome sets of Food for Special Medical Purposes designed for type 2 diabetes mellitus: a study protocol

BACKGROUND: The Chinese government stipulates all food for special medical purposes (FSMP) designed for specific diseases to be tested in clinical trials before approving it for registration. The process of developing core outcome sets (COSs), the minimum sets of outcomes supposed to be measured and reported, provides an economical and practical option for stakeholders to communicate and cooperate in conducting clinical trials as well as in reporting FSMP outcomes. This study uses type 2 diabetes mellitus (T2DM) as an example to develop COS for clinical trials of FSMP. METHODS: The COS for FSMP-T2DM will be divided into 3 phases and developed following COS-STAP and COS-STAD: (1) Generate a list of relevant outcomes identified from a systematic review, in which information sources will mainly include published studies, regulatory documentation, and qualitative interviews of stakeholders. The identified outcomes will be categorized using a conceptual framework and formatted into the first round of the Delphi survey questionnaire items. (2) At least 2 rounds of Delphi surveys will be performed among stakeholders to create the COS for FSMP-T2DM. Patients, clinical dietitians, physicians, COS researchers, journal editors, FSMP manufacturers, and regulatory representatives will be invited to score each outcome from aspects of importance. (3) Hold a face-to-face or online consensus meeting to refine the content of the COS for FSMP-T2DM. Key stakeholders will be invited to attend the meeting to discuss and agree on the final COS. DISCUSSION: We have prepared an alternative solution of the Likert scale selection, Delphi survey rounds, scoring group, and consensus definitions in case of an unexpected situation. TRIAL REGISTRATION: COMET (1547). Registered on March 23, 2020. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13063-023-07214-2.