The patient assessment of constipation-symptoms (PAC-SYM) questionnaire has become the standard approach to evaluate patient response outcomes (PROs) in clinical trials of constipation. PROs are particularly useful in functional gastrointestinal disorders. However, directly translating the PRO-derived data into clinical practice is not always feasible. The minimal important difference (MID) is the smallest difference in score in the outcome of interest that informed patients or proxies perceive as important, either beneficial or harmful, and leads the patient or clinician to consider a change in the management. Yiannakou et al 1 have provided a numeric value of the threshold for reduction in total PAC-SYM score to define a clinical response. This was generated using three methods. First, an anchor-based approach provides a comparison of changes on this PRO with changes documented with another "anchor" measure of clinical relevance for which a clinically important difference can be defined. The absolute approach to framing the MID has advantages over the relative approach. 2 Second, a distribution-based method estimated the MID using a specific multiplication of the SD and incorporated a reliability coefficient. Third, receiver operating characteristics (ROC) ACKNOWLEDG EMENT Declaration of personal interests: M. Camilleri received research support from Novatis, AstraZeneca, Elira, Novo Nordisk, Rhythm, NGM Biopharma, Allergan, Vibrant and Entra Health. He has a consultant and an advisory board member for BioKer, Shionogi, Ironwood, Allergan, AstraZeneca, Elobix AB, Shire, Takeda and Theravance. He also owns stocks and shares in Dignify Therapeutics anf Enterin. Y. Saito has served as an advisory board member for Ironwood and Synergy, and has received research funding from Salix.
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AUTHORSHIPGuarantor of the article: M. Camilleri.