TABLE 3.

Discrimination (Discrim) and item location parameters of all MDS-UPDRS Parts 2 + 3 items from fitting one IRT model

Items	Item Names	Discrim	0 to 1	1 to 2	2 to 3	3 to 4
2.1	Speech	1.235	0.668	0.588	2.017	4.146
2.2	Saliva and drooling	0.870	0.292	0.717	2.332	4.432
2.3	Chewing and swallowing	1.175	0.495	1.994	3.001	5.951
2.4	Eating tasks	1.634	0.470	0.890	2.329	3.641
2.5	Dressing	2.003	0.911	0.490	1.606	2.625
2.6	Hygiene	1.916	0.636	0.837	1.775	2.710
2.7	Handwriting	1.280	1.279	0.392	1.568	2.872
2.8	Doing hobbies and other activities	1.504	0.812	0.404	1.445	2.436
2.9	Turning in bed	1.714	0.701	0.722	1.718	2.588
2.10	Tremor	0.492	2.259	0.871	3.735	6.712
2.11	Getting out of bed	1.990	0.880	0.379	1.359	2.254
2.12	Walking and balance	1.798	1.077	0.461	1.250	2.374
2.13	Freezing	1.385	0.009	0.927	1.801	3.132
3.1	Speech	1.633	−0.87	0.71	2.127	3.646
3.2	Facial expression	1.610	1.392	0.244	1.864	3.441
3.3a	Rigidity—neck	1.363	0.559	0.780	2.220	3.788
3.3b	Rigidity—RUE	1.302	1.113	0.451	2.294	4.388
3.3c	Rigidity—LUE	1.340	0.978	0.486	2.176	4.133
3.3d	Rigidity—RLE	1.488	0.596	0.698	2.219	3.865
3.3e	Rigidity—LLE	1.508	0.551	0.658	2.100	3.756
3.4a	Finger tapping—right hand	1.796	1.300	0.137	1.412	3.029
3.4b	Finger tapping—left hand	1.922	1.221	0.003	1.204	2.795
3.5a	Hand movements—right hand	2.017	1.008	0.281	1.530	2.991
3.5b	Hand movements—left hand	1.947	1.025	0.285	1.514	3.065
3.6a	Pronation-supination—right hand	1.867	1.029	0.298	1.548	2.979
3.6b	Pronation-supination—left hand	1.841	1.084	0.152	1.349	2.804
3.7a	Toe tapping—right foot	1.945	0.987	0.321	1.459	2.738
3.7b	Toe tapping—left foot	1.953	1.041	0.146	1.243	2.524
3.8a	Leg agility—right leg	2.184	0.735	0.511	1.600	2.811
3.8b	Leg agility—left leg	2.224	0.776	0.382	1.410	2.662
3.9	Arising from chair	2.220	0.003	0.974	1.666	2.441
3.10	Gait	2.243	1.102	0.332	1.472	2.509
3.11	Freezing of gait	1.717	0.524	1.289	2.214	2.938
3.12	Postural stability	1.878	0.220	0.608	1.237	2.529
3.13	Posture	1.868	1.023	0.370	1.585	2.906
3.14	Global spontaneity of movement	2.202	1.221	0.079	1.222	2.629
3.15a	Postural tremor—right hand	0.532	0.525	3.832	6.903	11.149
3.15b	Postural tremor—left hand	0.601	0.517	3.573	6.505	9.943
3.16a	Kinetic tremor—right hand	0.517	1.168	4.782	8.418	12.139
3.16b	Kinetic tremor—left hand	0.523	0.970	4.315	7.949	11.264
3.17a	Rest tremor amplitude—RUE	0.453	0.884	3.096	6.056	10.336
3.17b	Rest tremor amplitude—LUE	0.542	0.910	2.883	5.664	9.312
3.17c	Rest tremor amplitude—RLE	0.529	2.630	4.774	7.785	11.998
3.17d	Rest tremor amplitude—LLE	0.599	2.655	4.482	7.154	10.553
3.17e	Rest tremor amplitude—lip/jaw	0.674	3.083	5.089	7.330	9.221
3.18	Constancy of rest tremor	0.365	0.627	1.901	4.213	6.762

Note: 11 tremor items with low and moderate discrimination parameters are in boldface.

Abbreviations: MDS-UPDRS, The Movement Disorder Society 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.