Objective: The minimal clinically important difference (MCID) of a patient-reported outcome measure (PROM) represents a threshold value of change in PROM score deemed to have an implication in clinical management. The MCID is frequently used to interpret the significance of results from clinical studies that use PROMs. However, an understanding of the many caveats of the MCID, as well as its strengths and limitations, is necessary. The objective of this article is to provide a review of the calculation, interpretation, and caveats of MCID.
Data sources: MEDLINE and PubMed Central.
Review methods: Literature search-including primary studies, review articles, and consensus statements-pertinent to the objectives of this review using PubMed.
Conclusions: The MCID of a PROM may vary depending on the patients and clinical context in which the PROM is given. The primary approaches for calculating MCID are distribution-based and anchor-based methods. Each methodology has strengths and limitations, and the ideal determination of a PROM MCID includes synthesis of results from both approaches. The MCID of a PROM is also not perfect in detecting patients experiencing a clinically important improvement, and this is reflected in its accuracy (eg, sensitivity and specificity).
Implications for practice: Interpretation or application of MCID requires consideration of all caveats underlying the MCID, including the patients in whom it was derived, the limitations of the methodologies used to calculate it, and its accuracy for identifying patients who have experienced clinically significant improvement.
Keywords: MCID; minimal clinically significant difference; outcomes; quality of life.