Minimal Important Difference (MID) of two commonly used outcome measures for foot problems

Table 1 Anchor-based calculations of MID for the VAS and the FHSQ

Outcome	Domain	0 to +1	+2 to +3	MID values	95% CI
Measure		n = 57	n = 40
VAS	Average	-1.1^§	-8.9^†	-7.8	-11.7 to -3.9
	1st Step	-1.9	-20.5	-18.6	-24.6 to -12.6
FHSQ	Pain	8.7	21.2	12.5	5.8 to 19.2
	Function	4.8	11.9	7.1	0.7 to 13.4
	Footwear	1.9^‡	-0.2	-2.1	-8.0 to 3.8
	GFH	8.3	7.9	-0.4	-7.1 to 6.4

Abbreviations: VAS = Visual Analogue Scale, FHSQ = Foot Health Status Questionnaire, MID = Minimal Important Difference, GFH = General Foot Health, CI = Confidence Interval.
Note: Three variables were initially not normally distributed, so outliers that were 3SDs from the mean were removed to ensure normalcy. Accordingly, some variables had a lower sample size due to this, which the following symbols represent: ^§n = 55, ^‡n = 56, ^†n = 39.

ISSN: 1757-1146