Journal of Patient-Reported Outcomes

Table 5 Scale and positioning of the PFDI-20 items according to the PCM and CTT

From: Internal structure and classification of pelvic floor dysfunction distress by PFDI-20 total score

		Scale
PCM		− 1.5	− 1	− 0.5	0	0.5	1	1.5	2	2.5	3	3.5	4	4.5
CTT		0	1 to 15						16 to 34		35 to 40
Item	Parameters
1	b1	1.79							0.63	0.80	0.90	0.96	0.98	0.99	1.00
	b2	1.24								0.54	0.70	0.82	0.89	0.93	0.96
2	b1	2.26							0.58	0.76	0.89	0.95	0.98	0.99	1.00
	b2	0.83								0.58	0.75	0.86	0.92	0.95	0.97
3	b1	2.74										0.57	0.68	0.78	0.85
4	b1	3.22											0.57	0.69	0.78
5	b1	1.37						0.55	0.73	0.86	0.93	0.97	0.99	1.00	1.00
	b2	1.22								0.59	0.73	0.83	0.90	0.94	0.96
6	b1	4.17													0.58
7	b1	1.35						0.64	0.80	0.91	0.96	0.98	0.99	1.00	1.00
	b2	0.56							0.58	0.73	0.84	0.91	0.94	0.97	0.98
8	b1	0.89						0.66	0.81	0.90	0.96	0.98	0.99	1.00	1.00
	b2	1.25								0.61	0.74	0.84	0.90	0.94	0.96
9	b1	3.50												0.62	0.73
10	b1	2.99											0.62	0.73	0.82
11	b1	1.90							0.65	0.81	0.91	0.96	0.99	0.99	1.00
	b2	0.93								0.61	0.76	0.86	0.92	0.95	0.97
12	b1	2.09							0.65	0.82	0.92	0.97	0.99	1.00	1.00
	b2	0.63								0.65	0.80	0.88	0.93	0.96	0.98
13	b1	0.72					0.57	0.74	0.86	0.94	0.97	0.99	1.00	1.00	1.00
	b2	0.89							0.56	0.70	0.81	0.88	0.93	0.96	0.97
14	b1	2.93											0.64	0.75	0.83
15	b1	0.88						0.66	0.80	0.90	0.96	0.98	0.99	1.00	1.00
	b2	1.30								0.60	0.73	0.83	0.89	0.93	0.96
16	b1	2.44							0.65	0.82	0.92	0.97	0.99	1.00	1.00
	b2	0.20								0.70	0.84	0.91	0.95	0.97	0.98
17	b1	1.74						0.64	0.81	0.92	0.97	0.99	0.99	1.00	1.00
	b2	0.00							0.66	0.81	0.89	0.94	0.97	0.98	0.99
18	b1	1.37						0.63	0.80	0.91	0.96	0.98	0.99	1.00	1.00
	b2	0.59							0.57	0.73	0.84	0.90	0.94	0.97	0.98
19	b1	2.92								0.65	0.82	0.92	0.97	0.99	1.00
	b2	0.72									0.70	0.84	0.91	0.95	0.97
20	b1	2.84							0.52	0.73	0.87	0.95	0.98	0.99	1.00
	b2	0.37								0.61	0.78	0.88	0.94	0.97	0.98

PFDI-20: Pelvic floor distress inventory. PCM: Partial credit model. CTT: Classical test theory. b1 and b2: difficulty parameters of the items. Values of parameters b1 and b2 < 0.5 were removed from the table for better visualization

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