TABLE 1.

Distribution-based measures suggested to determine minimal clinically important difference (MCID)

Measure	Definition	Suggested MCID
Effect size	Standardised measure of change obtained by dividing the difference in scores from baseline to post-treatment by the standard deviation of baseline scores	<0.20: no change 0.20–0.49: small change 0.50–0.79: moderate change ≥0.80: large change
Standard error of measurements	It represents the variation in patient-reported outcome scores attributed to instrument unreliability, in which a change smaller than the calculated sem is likely due to measurement error rather than a true change	Threshold values of 1 sem, 1.96 sem and 2.77 sem have been suggested
Standard deviation	Measure used to quantify the amount of variation or dispersion of a set of data values	≥0.5 sd
Coefficient of variation	Standardised measure of dispersion of a frequency distribution	≥1.65 CV
Minimal detectable change	The smallest threshold of change in scores that can be considered above the measurement error with a given level of confidence (usually 95% confidence)	≥MDC
Reliable change index	Statistic that determines the magnitude of change score necessary of a given self-report measure to be considered statistically reliable It is calculated by dividing the individual patient change in score by the square root of the sem	≥1.96