Minimally important difference of the Treatment Satisfaction with Medicines Questionnaire (SATMED-Q)

Table 4 Minimally Important Difference (MID), standard error of measurement (SEM) and effect size of the standardised SATMED-Q total and domain scores calculated for the sample of 456 patients to test psychometric properties of the instrument

				Distribution-based MID
SATMED-Q domain	SATMED-Q mean score at neutral satisfaction category of TSQM item #14	SATMED-Q mean score at satisfied/dissatisfied category of TSQM item #14	Anchor-based MID¹	SEM²	One-half SD	Effect size³
Treatment effectiveness	51.5 (20.8)	67.1 (19.9)	15.6	9.5	10.9	0.71
Convenience of use	57.8 (26.3)	72.9 (21.1)	15.1	8.6	11.6	0.65
Impact on daily living/activities	43.5 (21.3)	64.1 (22.3)	20.6	9.4	12.2	0,85
Medical care	69.9 (22.3)	80.1 (17.8)	10.3	8.1	11.9	0.43
General satisfaction	57.1 (22.2)	75.2 (19.0)	18.2	8.1	10.6	0.83
Undesirable side effects	76.5 (24.4)	88.0 (20.8)	11.5	5.9	10.0	0.58
Total score	59.3 (12.1)	72.7 (13.0)	13.4	5.9	7.4	0.91

Values are means (standard deviation). 1Computed as the raw difference between scores in neutral response and satisfied/dissatisfied categories of TSQM item #14 used as an anchor reference. 2 SEM = Standard error of measurement obtained by multiplying the standard deviation of each domain or the total score in the entire sample by the root square of 1 minus the coefficient of reliability (-Cronbach's α). 3Obtained by dividing the MID of the domain or total score by the standard deviation of the whole sample for that domain or total score. TSQM = Treatment Satisfaction Questionnaire for Medications. SATMED-Q = Satisfaction with Medicines Questionnaire. SD = standard deviation.

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