Patient Uncertainty Questionnaire-Rheumatology (PUQ-R): development and validation of a new patient-reported outcome instrument for systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) in a mixed methods study

Table 4 Traditional psychometrics scale-level results

	Data quality	Scaling assumptions				Targeting			Reliability		Item convergent – discriminant validity: ITC range
	Missing data %	Possible range (mid- point)	Actual score range	Mean (SD)	CITC range	Floor effect %	Ceiling effect %	Skewn.	Cronbach’s alpha	IIC mean	1	2	3	4	5
Symptoms & flares	7.52	14–56 (35)	14–56	35.29 (7.99)	0.44–0.69	0.72	0.72	−0.35	0.90	0.40	0.54–0.73	0.05–0.20	0.12–0.34	0.16–0.45	0.02–0.25
Medication	4.30	11–40 (27.50)	11–44	30.96 (6.77)	−0.35–0.71	0.72	3.94	−0.15	0.90	0.60	0.02–0.18	0.46–0.77	0.23–0.40	0.25–0.33	0.04–0.43
Trust in doctor	2.15	8–32 (20)	8–32	22.37 (4.90)	0.40–0.71	0.72	1.43	−0.24	0.86	0.61	0.32–0.14	0.23–0.49	0.56–0.78	0.39–0.20	0.24–0.49
Self-management	3.58	6–24 (15)	6–24	18.80 (3.68)	0.53–0.67	0.72	8.60	−0.61	0.82	0.60	0.18–0.48	0.19–0.44	0.26–0.40	0.67–0.78	0.04–0.21
Impact	2.51	10–40 (25)	10–40	24.95 (8.15)	0.39–0.79	1.43	0.36	−0.13	0.93	0.73	0.00–0.24	0.11–0.42	0.20–0.43	0.04–0.29	0.49–0.84

CITC corrected item total correlation, Skewn skewness statistic, IIC item-item correlation, ITC item total correlation

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