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

Table 2 HDISS-DU score: construct validity

Measure	Validity assessed	Spearman’s rho
Measure	Validity assessed	Baseline	Week 8	Week 16
Number of DUs	Convergent	0.01	0.10*	0.19**
SHAQ HAQ-DI grip domain score	Convergent	0.66***	0.71***	0.72***
SHAQ HAQ-DI hygiene domain score	Convergent	0.60***	0.64***	0.63***
SHAQ HAQ-DI eating domain score	Convergent	0.73***	0.77***	0.76***
SHAQ-DI dressing and grooming domain score	Convergent	0.69***	0.73***	0.73***
SHAQ VAS DU severity item score	Convergent	0.60***	0.60***	0.61***
Patient-reported severity	Convergent	0.57***	0.62***	0.64***
Physician-reported severity	Convergent	0.39***	0.37***	0.43***
WPAI:DU activity impairment	Convergent	0.63***	0.65***	0.72***
Global pain scale item score	Convergent	0.55***	0.61***	0.65***
SHAQ HAQ-DI arising domain score	Discriminant	0.39***	0.50***	0.50***
SHAQ HAQ-DI walking domain score	Discriminant	0.34***	0.47***	0.40***
SHAQ HAQ-DI reach domain score	Discriminant	0.56***	0.67***	0.63***
SHAQ VAS intestinal problems item score	Discriminant	0.23***	0.35***	0.33***
SHAQ VAS breathing problems item score	Discriminant	0.30***	0.39***	0.42***
WPAI:DU absenteeism	Discriminant	0.24*	0.26**	0.31**
WPAI:DU presenteeism	Discriminant	0.45***	0.55***	0.69**
WPAI:DU overall work impairment	Discriminant	0.45***	0.52***	0.66***

Spearman’s rank-order correlation assessed the association between the HDISS-DU score and other measures at baseline, week 8 and week 16. A priori hypotheses identified measures expected to capture similar concepts (assessed for convergent validity) and different concepts (assessed for discriminant validity) to the HDISS-DU score
*p < 0.05; **p < 0.01; ***p < 0.001
DU digital ulcer, HAQ-DI Health Assessment Questionnaire Disability Index, HDISS-DU Hand Disability in Systemic Sclerosis-Digital Ulcers, SHAQ Scleroderma Health Assessment Questionnaire, VAS visual analogue scale, WPAI:DU Work Productivity and Activity Impairment Questionnaire: Digital Ulcer

ISSN: 1478-6362