Understanding the Minimal Clinically Important Difference in Patient-Reported Outcomes

by Amy E. Hamaker •

Comment: In recent years, there has been an increased focus on placing patients at the center of health care research. Patient-reported outcomes are directly reported by the patient and pertain to the patient’s health, quality of life, or functional status. However, when considering patient-reported outcome measures (PROM), statistical significance does not necessarily equate to clinical significance. The concept of a minimal clinically important difference (MCID) is defined as the smallest difference in score, using a given measurement tool, in which patients identify a perceived benefit.

While conceptually straightforward, the author of this state-of-the-art review addresses the practical complexity of calculating the MCID. This article contains a useful overview of the two main methods for calculating MCID, broadly categorized as distribution-based and anchor-based methods. Furthermore, the author provides three key implications for practice. This article is a wonderful resource for researchers who are planning clinical studies with the intent to use the MCID as a benchmark for the magnitude of improvement. It also provides a thorough overview for practicing physicians, to assist them in their interpretation of the MCID within the broader literature and their own patient population.—Sarah Bowe, MD

How do you calculate and interpret the minimal clinically important difference (MCID) of patient-reported outcome measures (PROMs)?

BOTTOM LINE
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.

Background: The MCID of a 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.

Study design: Literature search including primary studies, review articles, and consensus statements.

Setting: MEDLINE and PubMed Central.

Synopsis: 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 (e.g., sensitivity and specificity).

Citation: Sedaghat AR. Understanding the minimal clinically important difference (MCID) of patient-reported outcome measures. Otolaryngol Head Neck Surg (published online ahead of print June 4, 2019). doi: 10.1177/0194599819852604