TABLE 5.
Discrimination (Discrim) and item location parameters of all MDS-UPDRS Parts 2 + 3 items from fitting two separate IRT models to 35 non-tremor items (Part 2 items 2.1–2.9, 2.11–2.13, and Part 3 items 3.1–3.14) and 11 tremor items (Part 2 item 2.10 and Part 3 items 3.15a–3.18)
| Items | Item Names | Discrim | 0 to 1 | 1 to 2 | 2 to 3 | 3 to 4 |
|---|---|---|---|---|---|---|
| 2.1 | Speech | 1.271 | 0.659 | 0.575 | 1.980 | 4.080 |
| 2.2 | Saliva and drooling | 0.884 | 0.291 | 0.706 | 2.302 | 4.379 |
| 2.3 | Chewing and swallowing | 1.180 | 0.493 | 1.987 | 2.994 | 5.943 |
| 2.4 | Eating tasks | 1.626 | 0.472 | 0.891 | 2.336 | 3.667 |
| 2.5 | Dressing | 2.037 | 0.905 | 0.484 | 1.593 | 2.610 |
| 2.6 | Hygiene | 1.947 | 0.632 | 0.829 | 1.761 | 2.694 |
| 2.7 | Handwriting | 1.286 | 1.278 | 0.390 | 1.564 | 2.867 |
| 2.8 | Doing hobbies and other activities | 1.524 | 0.807 | 0.400 | 1.434 | 2.418 |
| 2.9 | Turning in bed | 1.765 | 0.692 | 0.709 | 1.692 | 2.554 |
| 2.10 | Tremor | 1.479 | 0.929 | 0.467 | 1.639 | 2.766 |
| 2.11 | Getting out of bed | 2.047 | 0.870 | 0.372 | 1.341 | 2.226 |
| 2.12 | Walking and balance | 1.852 | 1.063 | 0.453 | 1.231 | 2.344 |
| 2.13 | Freezing | 1.426 | 0.005 | 0.908 | 1.768 | 3.082 |
| 3.1 | Speech | 1.663 | 0.863 | 0.700 | 2.106 | 3.630 |
| 3.2 | Facial expression | 1.603 | 1.397 | 0.241 | 1.866 | 3.460 |
| 3.3a | Rigidity—neck | 1.349 | 0.564 | 0.782 | 2.233 | 3.823 |
| 3.3b | Rigidity—RUE | 1.271 | 1.131 | 0.457 | 2.326 | 4.468 |
| 3.3c | Rigidity—LUE | 1.310 | 0.992 | 0.491 | 2.205 | 4.205 |
| 3.3d | Rigidity—RLE | 1.471 | 0.601 | 0.701 | 2.232 | 3.904 |
| 3.3e | Rigidity—LLE | 1.498 | 0.554 | 0.658 | 2.105 | 3.781 |
| 3.4a | Finger tapping—right hand | 1.772 | 1.309 | 0.137 | 1.420 | 3.056 |
| 3.4b | Finger tapping—left hand | 1.899 | 1.228 | 0.003 | 1.209 | 2.813 |
| 3.5a | Hand movements—right hand | 1.991 | 1.013 | 0.282 | 1.537 | 3.014 |
| 3.5b | Hand movements—left hand | 1.923 | 1.031 | 0.286 | 1.522 | 3.090 |
| 3.6a | Pronation-Supination—right hand | 1.840 | 1.036 | 0.299 | 1.556 | 3.004 |
| 3.6b | Pronation-Supination—left hand | 1.826 | 1.088 | 0.152 | 1.353 | 2.820 |
| 3.7a | Toe tapping—right foot | 1.941 | 0.988 | 0.320 | 1.459 | 2.745 |
| 3.7b | Toe tapping—left foot | 1.957 | 1.040 | 0.145 | 1.241 | 2.523 |
| 3.8a | Leg agility—right leg | 2.170 | 0.737 | 0.511 | 1.602 | 2.822 |
| 3.8b | Leg agility—left leg | 2.229 | 0.775 | 0.381 | 1.408 | 2.663 |
| 3.9 | Arising from chair | 2.252 | 0.005 | 0.963 | 1.652 | 2.430 |
| 3.10 | Gait | 2.274 | 1.097 | 0.327 | 1.462 | 2.499 |
| 3.11 | Freezing of gait | 1.745 | 0.517 | 1.275 | 2.194 | 2.918 |
| 3.12 | Postural stability | 1.908 | 0.221 | 0.599 | 1.224 | 2.513 |
| 3.13 | Posture | 1.869 | 1.024 | 0.366 | 1.582 | 2.911 |
| 3.14 | Global spontaneity of movement | 2.184 | 1.226 | 0.077 | 1.222 | 2.640 |
| 3.15a | Postural tremor—right hand | 2.168 | 0.249 | 1.450 | 2.435 | 3.714 |
| 3.15b | Postural tremor—left hand | 2.008 | 0.274 | 1.547 | 2.640 | 3.865 |
| 3.16a | Kinetic tremor—right hand | 1.845 | 0.506 | 1.840 | 3.050 | 4.255 |
| 3.16b | Kinetic tremor—left hand | 1.641 | 0.449 | 1.797 | 3.125 | 4.307 |
| 3.17a | Rest tremor amplitude—RUE | 2.704 | 0.337 | 0.990 | 1.745 | 2.736 |
| 3.17b | Rest tremor amplitude—LUE | 2.683 | 0.397 | 1.076 | 1.911 | 2.917 |
| 3.17c | Rest tremor amplitude—RLE | 2.264 | 1.020 | 1.726 | 2.632 | 3.852 |
| 3.17d | Rest tremor amplitude—LLE | 2.296 | 1.126 | 1.785 | 2.679 | 3.786 |
| 3.17e | Rest tremor amplitude—lip/jaw | 2.003 | 1.485 | 2.312 | 3.192 | 3.931 |
| 3.18 | Constancy of rest tremor | 3.076 | 0.099 | 0.568 | 1.079 | 1.551 |
Note: 11 tremor items with high and very high discrimination parameters are in boldface.
Abbreviations: MDS-UPDRS Movement Disorder Society-sponsored revision of the Unified Parkinson’s Disease Rating Scale; IRT, item response theory; RUE, right upper extremity; LUE, left upper extremity; RLE, right lower extremity; LLE, left lower extremity.