Rasch analysis of the Dutch version of the Oxford elbow score

Figures & data

Table 1 The 12 items of the Oxford elbow score

“During the past 4 weeks …”

Have you had difficulty lifting things in your home, such as putting out the rubbish, because of your elbow problem? Have you had difficulty carrying bags of shopping, because of your elbow problem? Have you had any difficulty washing yourself all over, because of your elbow problem? Have you had any difficulty dressing yourself, because of your elbow problem? Have you felt that your elbow problem is “controlling your life”? How much has your elbow problem been “on your mind”? Have you been troubled by pain from your elbow in bed at night? How often has your elbow pain interfered with your sleeping? How much has your elbow problem interfered with your usual work or everyday activities? Has your elbow problem limited your ability to take part in leisure activities that you enjoy doing? How would you describe the worst pain you had from your elbow? How would you describe the pain you usually had from your elbow?

Figure 1 Person (n = 146) and item (12 items) or Wright map for the Oxford elbow score scale. Positive scores indicate better quality of life, whereas negative scores indicate poorer quality of life. Items from the scale are shown on the right side of the figure, and person measures are highlighted by “#” or “.”

Notes: Each “#” represents two subjects, and each “.” represents one subject.
Abbreviations: M, mean; S, one standard deviation from the mean; T, two standard deviations from the mean.

Table 2 Item statistics, Oxford elbow score, Dutch version

Item	Count	Measure	Infit MNSQ	Outfit MNSQ
6	146	0.57	1.02	1.26
11	146	0.57	0.68	0.65
2	146	0.47	1.08	0.96
10	146	0.41	1.19	1.05
1	146	0.35	0.99	0.91
9	146	0.28	0.69	0.61
5	146	−0.01	0.89	0.89
7	146	−0.17	1.19	0.96
8	146	−0.36	1.11	0.99
3	146	−0.44	1.03	0.97
4	146	−0.66	0.81	0.85
12	144	−1.02	1.70	1.53

Figure 2 Category probability curve of the Dutch version of the Oxford elbow score scale showing the probability of assigning to any particular category (y axis) given the difference in estimates between any patient quality of life measurement and any item difficulty. The threshold estimates correspond to the intersection of rating scale categories.

Table 3 Summary of the category structure of the Oxford elbow score, Dutch version

Category label/score	Observed count	Observed count %	Observed average	Outfit mean square	Threshold
0	109	6	−0.99	1.14	none
1	276	16	−0.63	0.95	−1.77
2	258	15	0.38	0.67	−0.02
3	335	19	1.31	0.89	0.51
4	772	44	2.39	1.22	1.28