Psychometric validation of the Hand Disability in Systemic Sclerosis-Digital Ulcers (HDISS-DU®) patient-reported outcome instrument

Table 3 HDISS-DU score: known-group validity

	Group	Number	Mean HDISS-DU score (SE)	f value/t value	p value
Baseline	Number of DUs
	≤ 3	337	2.94 (0.06)	0.00	0.9854
	> 3	178	2.94 (0.08)	0.00	0.9854
	DU complications category
	None	512	2.94 (0.05)	4.96	0.0263
	Mild	3	4.34 (0.63)
	Moderate	0	N/A
	Severe	0	N/A
	Number of hands affected
	One	184	3.02 (0.08)	1.32	0.2505
	Two	331	2.90 (0.06)	1.32	0.2505
Week 8	Number of DUs
	≤ 3	276	2.75 (0.06)	2.39	0.1227
	> 3	152	2.92 (0.09)	2.39	0.1227
	DU complications category
	None	407	2.76 (0.05)	8.96	0.0002
	Mild	20	3.75 (0.24)
	Moderate	1	4.04 (1.05)
	Severe	0	N/A
	Number of hands affected
	One	156	2.83 (0.09)	0.14	0.7133
	Two	227	2.87 (0.07)	0.14	0.7133
Week 16	Number of DUs
	≤ 3	228	2.76 (0.07)	6.71	0.0100
	> 3	106	3.09 (0.10)	6.71	0.0100
	DU complications category
	None	306	2.83 (0.06)	7.85	0.0005
	Mild	16	2.64 (0.27)
	Moderate	0	N/A
	Severe	12	4.05 (0.31)
	Number of hands affected
	One	134	2.74 (0.09)	6.10	0.0141
	Two	159	3.05 (0.08)	6.10	0.0141

Known-group validity was assessed by independent samples t test (2 patient groups; t value) or by ANOVA (≥ 3 patient groups; f value)
ANOVA analysis of variance, DU digital ulcer, HDISS-DU Hand Disability in Systemic Sclerosis-Digital Ulcers, n number of participants, N/A not applicable, SE standard error

ISSN: 1478-6362