Table 3. Results of item response theory analysis, including scalability coefficients, item fit statistics, and item parameters for the 10 items of the biomedical scale of the Pain Attitudes and Beliefs Scale (PABS).

	MSA Hi	S-X2	p-value S-X2	α	β1	β2	β3	β4	β5
BeBack (n = 1016)
Item 1	0.257	104.497	0.158	1.076	-3.336	-1.594	-0.223	1.671	4.211
Item 2	0.244	123.924	0.004	1.029	-2.714	-0.328	1.293	2.512	4.552
Item 3	0.259	90.790	0.287	1.075	-2.163	-0.372	1.188	3.123	/
Item 4	0.222	122.820	0.113	0.807	-4.847	-2.403	-0.477	1.448	3.508
Item 5	0.204	102.813	0.251	0.719	-5.014	-1.822	-0.011	2.249	5.908
Item 6	0.304	119.913	0.023	1.259	-3.389	-1.432	-0.387	0.890	3.158
Item 7	0.369	80.860	0.045	2.452	-1.506	-0.143	0.919	1.863	/
Item 8	0.349	75.481	0.176	1.956	-1.666	-0.097	1.018	2.346	/
Item 9	0.325	93.763	0.025	1.731	-1.140	0.466	1.285	2.466	/
Item 10	0.209	99.163	0.157	0.749	-4.144	-0.809	0.572	3.121	6.137
DABS (n = 958)
Item 1	0.313	92.861	0.341	1.640	-2.337	-1.116	-0.313	1.006	2.815
Item 2	0.297	65.184	0.900	1.244	-2.255	-0.425	0.994	2.363	/
Item 3	0.287	129.931	<0.001	1.382	-1.953	-0.583	0.639	2.118	/
Item 4	0.194	117.774	0.036	0.644	-7.076	-4.436	-1.985	0.584	3.029
Item 5	0.198	123.035	0.138	0.584	-6.438	-2.916	-0.786	2.367	6.182
Item 6	0.246	108.498	0.130	0.784	-5.484	-2.972	-1.470	0.474	3.674
Item 7	0.380	50.165	0.813	2.421	-1.589	-0.179	0.807	1.790	/
Item 8	0.328	69.449	0.563	1.751	-1.924	-0.234	0.621	1.944	/
Item 9	0.347	96.614	0.023	1.766	-1.104	0.147	1.078	2.275	/
Item 10	0.162	145.038	0.040	0.438	-7.488	-3.726	-2.026	0.685	5.370

MSA H_i = Mokken scale analysis scalability coefficient; S-X² = item fit statistics under the graded response model; α = Item Discrimination Parameters estimated under the graded response model; β = Item Difficulty Parameters estimated under the graded response model. n = number; / = not applicable.