Table 2

Item parameters from the dichotomous Rasch model for the 20-Item Tophus Impact Questionnaire (TIQ-20)

Item number	Item description	Location	Residual	χ²	p Value
27	My life would be better if I could get rid of my tophi	−2.19	−0.26	0.01	1.00
25	My tophi are unpleasant to look at	−1.86	−0.17	0.71	0.70
2	I feel pain when my tophi are knocked	−1.74	−0.67	1.43	0.49
21	My tophi do not have any effect on my life	−1.58	1.11	1.51	0.47
28	My tophi do not bother me	−1.14	0.67	0.47	0.79
31	I have visited my doctor for treatment of my tophi	−0.90	1.57	6.60	0.04
22	I feel embarrassed because of my tophi	−0.54	−1.65	3.58	0.17
11	I have to make changes to my footwear because of my tophi	−0.34	−0.61	0.64	0.73
1	My tophi are painful	−0.03	−0.93	0.76	0.68
20	I cannot play sport because of my tophi	0.13	−2.04	5.83	0.05
3	I have difficulty walking because of my tophi	0.25	−0.66	0.96	0.62
13	My tophi cause financial difficulty	0.43	−0.34	0.30	0.86
23	My tophi cause others to feel uncomfortable	0.44	−0.26	0.61	0.74
7	Writing is difficult because of my tophi	0.63	−0.66	0.46	0.79
14	My tophi cause difficulty participating in family life	0.90	−1.85	4.20	0.12
12	I have to buy special shoes because of my tophi	1.13	−1.16	1.53	0.47
6	Bending down to the ground is difficult because of my tophi	1.31	−1.10	1.47	0.48
30	My tophi have become infected	1.39	0.50	2.56	0.28
32	I have had surgery for my tophi	1.81	0.45	7.78	0.02
8	I have difficulty feeding myself because of my tophi	2.16	−1.09	3.04	0.22

Items are ordered by difficulty (more negative items indicate ‘easier’ items, that is, affirmative responses mean relatively less burden in comparison with more positive items for which affirmative items mean relatively more tophus burden). A Bonferroni corrected p value of 0.0025 was statistically significant.