A patient-reported pressure ulcer health-related quality of life instrument for use in prevention trials (PU-QOL-P): psychometric evaluation

Table 1 PU-QOL-P scale level analyses - Reliability and scaling assumptions: Validity within-scale analysis

PU-QOL-P scale (n items)	Internal consistency		Mean inter-item correlation	Inter-item correlation^a	Scaling Assumptions -Corrected ITC^a
PU-QOL-P scale (n items)	N^c	Cronbach’s alpha	Mean inter-item correlation	Inter-item correlation^a	Scaling Assumptions -Corrected ITC^a
Pain (12)	617	0.864	0.355	0.128–0.713	0.364–0.642
Exudate (8)	60^b	0.860	0.451	−0.024 – 0.865	0.337–0.824
Odour (6)	61^b	0.795	0.492	−0.017 – 1.000	− 0.017 – 0.893
Sleep (7)	333	0.937	0.682	0.540–0.827	0.753–0.871
Movement & mobility (9)	177	0.963	0.744	0.593–0.928	0.803–0.909
Daily activities (6)	186	0.937	0.705	0.476–0.900	0.581–0.914
Malaise (5)	215	0.915	0.680	0.559–0.844	0.669–0.846
Emotional well-being (15)	220	0.970	0.681	0.447–0.900	0.630–0.869
Self-consciousness and appearance (7)	305	0.921	0.645	0.532–0.786	0.695–0.818

SEM standard error mean; IIC inter-item correlation; ITC item-total correlation (corrected for overlap)
^aRange
^bsample n = 62; only patients with a category ≥2 PU complete exudate and odour scale
^cn estimated based on listwise deletion; observations that have one or more missing values across all variables are removed from analysis