Table 2.

Physical Domain (10 items) - Overview of final SF-HDQ item level and domain model fit statistics

Item #	Final SF-HDQ items	Item level statistics
Physical domain		Location	SE	Residual	ChiSq χ2	p value
1	Fatigue	− 0.694	0.038	− 0.276	13.544	0.140
3	Nauseaa	0.132	0.044	− 0.748	18.549	0.029
4	Headaches	0.098	0.039	0.361	16.422	0.059
5	Numbness or tingling in hands	0.288	0.039	0.100	8.470	0.488
7	Aches or pains	− 0.441	0.036	− 1.399	21.204	0.012
10	Shortness of breath	0.240	0.041	0.061	15.153	0.087
11	Fever, chills, or sweats	0.162	0.039	− 0.529	18.191	0.033
13	Muscle cramps	0.262	0.040	− 2.120	13.636	0.136
17	Trouble sleeping	− 0.761	0.034	2.141	14.346	0.111
20	Feel dizzy	0.714	0.045	− 1.555	14.747	0.098
Final model: physical domain—10 items (raw score range: 0–39)
Mean		− 1.137
Standard deviation		0.980
Sample size		981
Chi-square statistic (df) p value		154.2609 (df: 90) p = 0.0003
Cronbach’s alpha		0.84762
Person Separation Index		0.79042
Unidimensionality t-test (% significant)		0.41%
Differential Item Functioning  (DIF)		None

^aHDQ3 rescored to 4 response categories (0–3)