Psychometric validation and meaningful change thresholds of the Worst Itching Intensity Numerical Rating Scale for assessing itch in patients with chronic kidney disease-associated pruritus

Journal of Patient-Reported Outcomes

Table 3 Construct validity

Comparator measure	Domains	Pearson correlation with WI-NRS
		Baseline^a		End of treatment
		Pearson r	P-value	Pearson r	P-value
Phase 2 cohort
5-D itch	Total score	0.31	< 0.0001	0.71	< 0.0001
	Degree	0.30	< 0.0001	0.67	< 0.0001
	Duration	0.22	< 0.01	0.46	< 0.0001
	Direction	0.12	NS	0.51	< 0.0001
	Disability	0.33	< 0.0001	0.56	< 0.0001
	Distribution	0.14	NS	0.37	< 0.0001
Skindex-10	Total score	0.32	< 0.0001	0.67	< 0.0001
	Disease domain	0.34	< 0.0001	0.80	< 0.0001
	Mood-emotional distress	0.35	< 0.0001	0.61	< 0.0001
	Social functioning	0.21	< 0.01	0.48	< 0.0001
PGI-S	–	0.29	< 0.001	0.63	< 0.0001
MOS sleep	Sleep Problem Index I	0.20	< 0.01	0.18	< 0.05
	Sleep Problem Index II	0.17	< 0.05	0.26	< 0.01
	Sleep Disturbance	0.16	< 0.05	0.23	< 0.01
Phase 3 cohort
5-D itch	Total score	0.47	< 0.0001	0.70	< 0.0001
	Degree	0.41	< 0.0001	0.65	< 0.0001
	Duration	0.39	< 0.0001	0.52	< 0.0001
	Direction	0.23	< 0.0001	0.59	< 0.0001
	Disability	0.33	< 0.0001	0.53	< 0.0001
	Distribution	0.25	< 0.0001	0.43	< 0.0001
Skindex-10	Total score	0.41	< 0.0001	0.66	< 0.0001
	Disease domain	0.43	< 0.0001	0.70	< 0.0001
	Mood-emotional distress	0.37	< 0.0001	0.60	< 0.0001
	Social functioning	0.33	< 0.0001	0.54	< 0.0001

MOS, Medical Outcomes Study; NS, not significant; PGI-S, Patient Global Impression of Worst Itch Severity; WI-NRS, Worst Itching Intensity Numerical Rating Scale
^aPre-treatment on day 1, baseline