Development and validation of the patient-reported outcome for older people living with HIV/AIDS in China (PROHIV-OLD)

Table 6 Item reduction based on IRT

Item No.	α	Disordered threshold	Non-uniform DIF	Uniform DIF	Outcome
Factor 1
44	2.04	—	—	—	√
45	2.14	—	—	—	√
46	1.27	—	income	income	×
47	0.97	—	—	—	√
49	2.79	—	—	residence, income	√
50	1.45	—	—	residence	√
53	2.72	—	—	—	√
54	3.01	—	—	—	√
Factor 2
1	2.91	—	—	—	√
2	1.86	—	—	—	√
6	1.49	disordered	—	—	×
7	1.95	—	residence	residence, income	×
10	1.79	—	—	residence	√
11	2.95	—	—	—	√
12	2.15	—	—	—	√
55	1.58	—	—	—	√
Factor 3
13	2.53	—	—	—	√
15	2.85	—	—	—	√
16	2.87	—	—	—	√
25	1.89	disordered	—	—	×
26	1.72	—	—	—	√
27	1.87	—	residence, income	—	×
28	1.49	—	—	—	√
Factor 4
31	51.45^a	abnormal distribution	—	—	×
32	1.58	—	—	—	√
34	2.58	—	—	—	√
35	2.29^a	—	—	—	√
38	5.09	—	—	—	×
Factor 5
19	1.86	—	—	—	√
20	1.95	—	—	—	√
21	2.15	—	—	—	√
22	1.51	disordered	gender	—	×
23	1.74	—	—	—	√

—: no detection of disordered threshold or DIF
^a: results of the second item analysis
√: represented the selected item, ×: indicated the item considered to be deleted

ISSN: 1477-7525