Table 3.

Differential Item Functioning Analysis Results

	LRT p-value		ΔR2
	M1 vs. M2	M2 vs. M3	M1 vs. M2	M2 vs. M3
Full sample
Physical Function	.013–.814	.249–.978	.000–.010	.001–.002
Fatigue	.197–.938	.096–.816	.000–.002	.000–.003
Pain Interference	.501–.966	.132–.945	.000–.006	.000–.003
Anger	.168–.990	.037–.779	.000–.003	.000–.006
Anxiety	.075–.618	.117–.721	.000–.004	.000–.004
Depression	.029–.456	.111–.928	.001–.008	.000–.004
Emotional Support	.041–.890	.094–.932	.000–.005	.000–.004
SCI subsample
Physical Function	.056–.768	.025–.885	.000–.027	.000–.013
Fatigue	.072–.960	.164–.846	.000–.008	.000–.005
Pain Interference	.004–.892	.032–.929	.000–.019	.000–.010
Anger	.033–.989	.009–.971	.000–.015	.000–.017
Anxiety	.021–.855	.199–.926	.000–.018	.000–.004
Depression	.140–.952	.042–.924	.000–.008	.000–.013
Emotional Support	.039–.980	.058–.873	.000–.011	.000–.010
TBI subsample
Physical Function	.148–.873	.050–.998	.000–.013	.000–.022
Fatigue	.043–.835	.007–.777	.000–.015	.000–.022
Pain Interference	.064–.893	.305–.888	.000–.018	.000–.004
Anger	.191–.954	.016–.834	.000–.005	.000–.021
Anxiety	.120–.987	.021–.882	.000–.009	.000–.020
Depression	.001–.544	.348–.683	.002–.031	.001–.004
Emotional Support	.077–.880	.333–.879	.000–.012	.000–.003

Note: All values correspond to ranges across all items for a given PROMIS measure. M1 = Baseline OLR model. M2 = Uniform DIF OLR model. M3 = Non-uniform DIF OLR model. LRT p-value = p-value for LRT comparing two models. ΔR² = difference in McFadden’s R² between two models.