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