Table 1

Item calibrations with standard error (SE), infit statistics, and outfit statistics for the items of the Dutch WOMAC and the English WOMAC pain and physical functioning dimensions, according to the item order of the WOMAC

WOMAC	Dutch				English
WOMAC	Calibration	SE	Infit	Outfit	Calibration	SE	Infit	Outfit
Calibrations are expressed in logits. Negative calibrations indicate easier items; positive calibrations indicate more difficult items.
Infit and outfit statistics >1.30 indicate items that do not contribute to the underlying construct. Statistics >1.30 are shown in italics. Infit and outfit statistics <0.70 indicate items that are muted.
Pain
1. Walking on a flat surface	−0.47	0.13	1.10	1.11	−0.11	0.10	0.78	0.80
2. Going up or down stairs	−1.14	0.14	0.90	0.89	−1.19	0.10	0.92	0.91
3. At night while in bed	0.63	0.13	1.31	1.29	0.28	0.10	1.23	1.24
4. Sitting or lying	0.85	0.13	0.73	0.73	1.03	0.10	0.83	0.82
5. Standing upright	0.13	0.13	0.85	0.83	−0.01	0.10	1.19	1.18
Physical functioning
8. Descending stairs	0.27	0.12	1.04	1.03	0.19	0.10	0.98	0.97
9. Ascending stairs	−0.65	0.12	0.94	0.91	−0.58	0.10	0.83	0.84
10. Rising from sitting	0.00	0.12	0.58	0.57	−0.01	0.10	0.90	0.92
11. Standing	0.32	0.12	1.16	1.16	0.39	0.10	0.97	0.97
12. Bending to floor	−1.09	0.12	1.24	1.21	−0.77	0.10	1.02	0.97
13. Walking on flat	0.41	0.12	1.13	1.14	0.33	0.10	0.82	0.81
14. Getting in/out of car	−0.91	0.12	0.78	0.77	−0.69	0.10	0.67	0.68
15. Going shopping	−0.87	0.12	0.91	0.88	−0.90	0.10	0.80	0.77
16. Putting on socks/stockings	−0.82	0.12	1.56	1.51	−0.94	0.10	1.29	1.27
17. Rising from bed	0.56	0.12	0.71	0.70	0.59	0.10	0.76	0.76
18. Taking off socks/stockings	−0.14	0.12	1.20	1.18	−0.17	0.10	1.17	1.18
19. Lying in bed	1.29	0.12	1.23	1.21	0.99	0.09	1.35	1.34
20. Getting in/out of bath	0.28	0.14	1.10	1.11	−0.20	0.10	1.16	1.24
21. Sitting	1.54	0.12	1.00	0.96	1.56	0.09	0.96	0.98
22. Getting on/off toilet	0.51	0.12	0.68	0.67	1.03	0.09	1.11	1.09
23. Heavy domestic duties	−1.56	0.13	0.85	0.87	−1.72	0.10	1.11	1.06
24. Light domestic duties	0.86	0.12	0.73	0.73	0.90	0.09	1.04	1.02