Table 3.

Comparison of Linking Methods

	Correlation	Mean Difference	Standard Deviation of Difference	Root Mean Squared Deviation
BPI-PI to PROMIS-PI
IRT pattern scoring	0.904	−0.012	4.014	4.014
IRT crosswalk	0.904	0.188	4.007	4.012
EQP raw-scale SM=0.0	0.902	0.271	4.120	4.129
EQP raw-scale SM=0.3	0.903	0.173	4.093	4.096
EQP raw-scale SM=1.0	0.904	0.120	4.039	4.041
SF36-BP to PROMIS-PI
IRT pattern scoring	0.860	−0.165	4.667	4.668
IRT crosswalk	0.852	−0.132	4.785	4.787
EQP raw-scale SM=0.0	0.850	−0.095	4.860	4.861
EQP raw-scale SM=0.3	0.840	0.720	5.445	5.492
EQP raw-scale SM=1.0	0.836	0.958	5.678	5.759

BPI-PI = Brief Pain Inventory Pain Interference; PROMIS-PI = Patient Reported Outcomes Measurement Information System Pain Interference Scale; SF36-BP = Short Form-36 Bodily Pain; IRT = item response theory; EAP=Expected a priori; EQP = equipercentile