Minimal important changes in standard deviation units are highly variable and no universally applicable value can be...

Area of Science:

• Clinical trial methodology
• Health outcomes research
• Statistical analysis in medicine

Background:

• Minimal important change (MIC) is crucial for interpreting clinical trial results.
• Standardizing MIC estimates in standard deviation (SD) units aids cross-study comparisons.
• Understanding the distribution and robustness of MIC estimates is essential for evidence-based medicine.

Purpose of the Study:

• To describe the distribution of anchor-based minimal important change (MIC) estimates in standard deviation (SD) units.
• To examine the influence of different SD metrics (baseline, endpoint, change) on MIC estimates.
• To assess the impact of methodological credibility on the robustness of MIC estimates.

Main Methods:

• Systematic review of anchor-based MIC estimates from MEDLINE and other literature databases up to October 2018.
• Conversion of MIC estimates to SD units using baseline, endpoint, and change from baseline SDs.
• Descriptive analysis of MIC distributions and sensitivity analysis excluding low-credibility estimates.

Main Results:

• Included 1,009 MIC estimates from 182 studies.
• Median MICs in SD units were 0.43 (baseline SD), 0.42 (endpoint SD), and 0.51 (change SD).
• Distributions showed wide variability, with over half of estimates between 0.2 and 0.8 SD, and remained stable after excluding less credible methods.

Conclusions:

• A universally applicable minimal important change (MIC) in standard deviation (SD) units could not be determined.
• Anchor-based MIC estimates in SD units exhibit wide distribution regardless of the SD metric or methodological rigor.
• The findings highlight the variability in MIC estimates and the need for cautious interpretation in clinical practice and research.