Table 3.

Item response model parameters and differential item functioning.

	ai (SE)	bi (SE)	P for DIF*
			a i	b i
Course of disease	0.56 (0.14)	0.66 (0.22)	0.73	0.60
Nephropathy	0.27 (0.19)	7.81 (5.42)	0.43	0.01
Retinopathy	0.43 (0.14)	2.22 (0.73)	0.10	0.14
Previous ulceration	1.45 (0.33)	2.25 (0.34)	0.27	0.28
Presence of skin changes	1.31 (0.28)	2.10 (0.31)	0.92	0.34
Fungal infection of skin	0.54 (0.16)	2.58 (0.72)	0.15	0.43
Callus/corn	0.82 (0.21)	2.56 (0.55)	0.87	0.15
Structural deformity	0.98 (0.20)	1.58 (0.26)	0.78	0.01
Fungal toenail	0.93 (0.17)	0.77 (0.15)	0.03	0.47
Abnormal foot skin temperature	1.27 (0.24)	1.37 (0.19)	0.02	0.87
Dorsalis pedis pulse diminution	1.43 (0.25)	0.68 (0.11)	0.24	0.34
Loss of protective sensation	1.69 (0.27)	0.88 (0.11)	0.96	0.96

a_i: discrimination parameter; b_i: difficulty parameter; SE: standard error. DIF: differential item functioning.

^*P values of chi-square tests to examine differential item functioning with respect to gender-specific discrimination (a_i) and difficulty (b_i) parameters.