Table 4 Overall fit statistics for the aDSWAL-QoL scale
Analysis | Item-person interaction | Item-trait interaction | Reliability | Unidimensionality | % ext | |||
|---|---|---|---|---|---|---|---|---|
Scale | Initial scale (#items) Rescaled scale (suggestions by the Rasch model to improve model fit) (# items after adjustments) | Item FR Mean (SD) | Person FR Mean (SD) | χ2 (df) | p | PSI +ext/÷ ext | t-test %, (95%CI) |  |
Total scale | IS Total scale (44) | 0.19 (1.95) | −0.01 (1.64) | 302.65 (44) | <0.001 | 0.93/0.93 | 17.59 (13.5-21.7) | 0 |
RS Total scale (rescore 43 items, delete 7 misfit items, DIF-split 5 items) (42) | −0.19 (0.95) | −0.46 (1.86) | 50.96 (42) | 0.137 | 0.92/0.92 | NA | 0 | |
General burden | IS General burden (2) | 0.17 (0.10) | −0.57 (0.86) | 1.58 (2) | 0.453 | 0.69/0.51 | NA | 38.9 |
Eating duration | IS Eating duration (2) | −0.12 (0.32) | −0.29 (0.62) | 3.95 (2) | 0.139 | 0.70/0.42 | NA | 24.5 |
RS Eating duration (rescore 1 item + DIF-split 1 item) (3) | 0.06 (0.16) | −0.29 (0.60) | 2.70 (3) | 0.440 | 0.68/0.37 | NA | 24.5 | |
Eating desire | IS Eating desire (3) | 0.32 (0.51) | −0.24 (0.80) | 6.17 (3) | 0.104 | 0.61/0.40 | NA | 2.8 |
RS Eating desire (rescore 3 items) (3) | 0.37 (0.35) | −0.22 (0.73) | 10.75 (3) | 0.013 | 0.57/0.32 | NA | 10.2 | |
Symptoms | IS Symptoms (14) | −0.05 (0.88) | −0.29 (1.25) | 10.23 (14) | 0.741 | 0.87/0.86 | 10.8 (6.6-15.0) | 2.8 |
RS Symptoms (rescore 9 items) (14) | −0.08 (0.64) | −0.29 (1.17) | 12.02 (14) | 0.605 | 0.86/0.85 | 11.8 (7.5-16.0) | 2.8 | |
Food selection | IS Food selection (2) | 0.74 (0.77) | −0.10 (0.67) | 5.21 (2) | 0.074 | −0.44/-1.31 | NA | 29.9 |
RS Food selection (rescore 2 items) (2) | 0.82 (0.78) | −0.10 (0.55) | 1.11 (2) | 0.574 | −0.39/-1.33 | NA | 29.9 | |
Communication | IS Communication (2) | 0.25 (0.24) | −1.09 (1.57) | 2.44 (2) | 0.295 | 0.46/0.18 | NA | 18.1 |
RS Communication (rescore 1 item) (2) | 0.39 (1.47) | −1.14 (1.89) | 1.12 (2) | 0.570 | 0.43/-0.03 | NA | 27.6 | |
Fear of eating | IS Fear of eating (4) | 0.82 (1.65) | −0.36 (1.37) | 57.75 (4) | <0.001 | 0.26/0.23 | NA | 3.8 |
RS Fear of eating (rescore 2 items + delete 1 misfit item) (3) | 0.66 (0.58) | −0.19 (1.06) | 7.01 (3) | 0.072 | 0.15/-0.31 | NA | 38.6 | |
Mental health | IS Mental health (5) | −0.02 (0.83) | −0.48 (1.20) | 4.46 (5) | 0.486 | 0.71/0.72 | NA | 22.6 |
RS Mental health (rescore 4 items) (5) | 0.08 (0.91) | −0.41 (1.02) | 6.66 (5) | 0.247 | 0.73/0.72 | NA | 24.5 | |
Social functioning | IS Social functioning (5) | 0.08 (0.70) | −0.24 (0.96) | 11.93 (5) | 0.036 | 0.50/0.39 | NA | 31.8 |
RS Social functioning (rescore 5 items) (5) | 0.35 (0.81) | −0.49 (1.49) | 3.801 (5) | 0.578 | 0.62/0.46 | NA | 31.8 | |
Fatigue | IS Fatigue (3) | 0.12 (0.66) | −0.49 (1.03) | 1.64 (3) | 0.651 | 0.70/0.60 | NA | 14.3 |
Sleep | IS Sleep (2) | 0.37 (0.10) | −0.38 (0.82) | 3.15 (2) | 0.207 | 0.43/0.03 | NA | 29.5 |
RS Sleep (rescore 1 item) (2) | 0.13 (1.40) | −0.29 (0.72) | 2.50 (2) | 0.287 | 0.39/-0.06 | NA | 35.2 | |
Satisfactory fit | 0.00 (<1.40) | 0.00 (<1.40) |  | >0.05 | ≥0.70 | <5% or LCI ≤5% |  | |