Estimating the minimum important change in the 15D scores.

Area of Science:

• Health Outcomes Research
• Psychometrics
• Quality of Life Measurement

Background:

• The 15D is a generic, preference-based instrument for measuring health-related quality of life (HRQoL).
• Interpreting the clinical significance of changes in 15D scores requires established thresholds.
• A global assessment scale (GAS) can serve as an external anchor for determining minimum important change (MIC).

Purpose of the Study:

• To establish the minimum important change (MIC) for the 15D instrument.
• To facilitate the interpretation of empirical results derived from 15D scores.
• To define thresholds for clinically meaningful improvements and deteriorations in HRQoL as measured by the 15D.

Main Methods:

• A large cohort of 4,903 hospital patients across 16 disease entities participated.
• HRQoL was assessed using the 15D at baseline and 6 months post-treatment.
• A subjective five-category global assessment scale (GAS) was used to rate overall health status changes.
• Regression analysis and ROC curve analysis were employed to determine MIC thresholds.

Main Results:

• The study identified specific intervals for classifying 15D score changes into GAS categories.
• The generic MIC thresholds for improvement and deterioration were determined to be ±0.015.
• These thresholds represent the lower and upper limits for meaningful changes in 15D scores.

Conclusions:

• The generic minimum important change (MIC) for the 15D instrument is ±0.015.
• Future studies using the 15D should report mean score changes, statistical significance, and their relation to the MIC.
• Reporting the distribution of 15D score changes across GAS categories is recommended for comprehensive interpretation.