. Author manuscript; available in PMC: 2020 Nov 1.

Published in final edited form as: Qual Life Res. 2019 Jul 26;28(11):3117–3135. doi: 10.1007/s11136-019-02250-5

Table 4:

Estimated Item parameters for Graded Response Model: Comparison of Age (less than 65 vs 65 or more)

ICH-CAHPS Items		Slope	Thresholds			DIF test: Chi-square (p-value)
ICH-CAHPS Items		a	b₁	b₂	b₃	a DIF	b DIF
Nephrologist Communication and Caring (6 items), DTF = 0.0111
Items Candidate for DIF (Wald-1 estimates)
Q4: Doctor explains things	Young	3.09	−1.81	−0.78	−0.20	NS	12 (0.007)
Q4: Doctor explains things	Older	2.79	−1.56	−0.74	−0.03	NS	12 (0.007)
Q7: Doctor cared about you	Young	4.25	−1.78	−0.82	−0.32	4.4 (0.036)	NS
Q7: Doctor cared about you	Older	3.25	−1.97	−1.02	−0.41	4.4 (0.036)	NS
Items identified as Anchor (Wald-2 anchor selection estimates)
Q3: Doctor listens carefully	Young	3.75	−2.05	−0.92	−0.29	NS	NS
Q3: Doctor listens carefully	Older	3.68	−2.16	−0.96	−0.30	NS	NS
Q5: Doctor shows respect	Young	3.21	−2.10	−1.04	−0.41	NS	NS
Q5: Doctor shows respect	Older	4.00	−1.79	−0.98	−0.44	NS	NS
Q6: Doctor spends enough time	Female	2.92	−1.73	−0.54	0.13	NS	NS
Q6: Doctor spends enough time	Male	3.44	−1.67	−0.56	0.12	NS	NS
Q10: Doctor seemed informed	Young	2.07	−1.23			NS	NS
Q10: Doctor seemed informed	Older	2.11	−1.34			NS	NS
Quality of Dialysis Facility Care and Operations (17 items), No DIF candidate item found, DTF = 0.0514
Q11: Staff listens carefully	Young	3.53	−2.27	−1.01	−0.27	NS	NS
Q11: Staff listens carefully	Older	3.79	−2.04	−1.03	−0.32	NS	NS
Q12: Staff explains in a way that is easy to understand	Young	3.13	−1.92	−1.09	−0.31	NS	NS
Q12: Staff explains in a way that is easy to understand	Older	2.89	−1.94	−0.95	−0.17	NS	NS
Q13: Staff shows respect	Young	4.00	−2.10	−0.95	−0.34	NS	NS
Q13: Staff shows respect	Older	4.03	−1.93	−1.05	−0.30	NS	NS
Q14 Staff spent enough time	Young	3.17	−2.03	−0.91	−0.09	NS	NS
Q14 Staff spent enough time	Older	3.51	−1.88	−0.84	−0.07	NS	NS
Q15: Staff cared about you	Young	4.02	−1.89	−0.96	−0.31	NS	NS
Q15: Staff cared about you	Older	3.89	−1.93	−0.98	−0.33	NS	NS
Q16: Staff makes you comfortable	Young	3.54	−2.37	−1.21	−0.43	NS	NS
Q16: Staff makes you comfortable	Older	3.40	−2.27	−1.25	−0.54	NS	NS
Q17: Staff keep information private	Young	1.31	−2.49			NS	NS
Q17: Staff keep information private	Older	1.40	−2.50			NS	NS
Q20: Comfortable asking staff	Young	1.90	−1.96			NS	NS
Q20: Comfortable asking staff	Older	2.07	−1.83			NS	NS
Q24: Staff inserts needle w/o pain	Young	0.99	−3.77	−1.10	0.62	NS	NS
Q24: Staff inserts needle w/o pain	Older	1.08	−3.34	−1.14	0.43	NS	NS
Q25: Staff checks you closely	Young	2.46	−2.64	−1.21	−0.20	NS	NS
Q25: Staff checks you closely	Older	2.19	−2.70	−1.26	−0.30	NS	NS
Q27: Staff manages problems	Young	2.76	−2.60	−1.29	−0.58	NS	NS
Q27: Staff manages problems	Older	2.75	−2.66	−1.31	−0.66	NS	NS
Q29: Staff behaves professionally	Young	2.57	−2.43	−1.41	−0.52	NS	NS
Q29: Staff behaves professionally	Older	2.29	−2.59	−1.53	−0.64	NS	NS
Q31 rev: Staff explains test result	Young	1.63	−0.42			NS	NS
Q31 rev: Staff explains test result	Older	1.68	−0.27			NS	NS
Q32: Staff discuss diet enough	Young	1.05	−2.39			NS	NS
Q32: Staff discuss diet enough	Older	1.40	−1.96			NS	NS
Q40: On machine within 15 minutes	Young	1.01	−3.82	−1.42	0.37	NS	NS
Q40: On machine within 15 minutes	Older	0.95	−3.74	−1.21	0.54	NS	NS
Q42: Center is clean	Young	1.39	−3.82	−2.01	−0.55	NS	NS
Q42: Center is clean	Older	1.17	−4.46	−2.67	−0.88	NS	NS
Q51: Satisfied with ways problems handled	Young	1.59	−1.94	−0.57	0.66	NS	NS
Q51: Satisfied with ways problems handled	Older	1.27	−2.34	−0.36	0.69	NS	NS
Providing Information to Patients (9 items), DTF = 0.0211
Items Candidate for DIF (Wald-1 estimates)
Q22: Knows to take care of dialysis connection	Young	1.09	−2.07			NS	8.6 (0.003)
Q22: Knows to take care of dialysis connection	Older	1.04	−1.62			NS	8.6 (0.003)
Q36: Staff told you how to get off machine if emergency	Young	0.50	−2.94			NS	4.6 (0.032)
Q36: Staff told you how to get off machine if emergency	Older	0.74	−1.62			NS	4.6 (0.032)
Items identified as Anchor (Wald-2 anchor selection estimates)
Q33: Staff gives information on patient rights	Young	2.28	−1.04			NS	NS
Q33: Staff gives information on patient rights	Older	1.40	−1.69			NS	NS
Q34: Staff reviews patient rights	Young	1.90	−0.54			NS	NS
Q34: Staff reviews patient rights	Older	1.29	−0.77			NS	NS
Q35: Staff told you what to do if health problem at home	Young	1.22	−1.10			NS	NS
Q35: Staff told you what to do if health problem at home	Older	1.85	−0.84			NS	NS
Q44: They talked about Which treatment is right for you	Young	1.80	−0.70			NS	NS
Q44: They talked about Which treatment is right for you	Older	3.01	−0.59			NS	NS
Q46: They explain why you are not eligible for transplant	Young	1.26	0.24			NS	NS
Q46: They explain why you are not eligible for transplant	Older	1.18	−0.09			NS	NS
Q47: Talk about peritoneal dialysis	Young	0.85	0.35			NS	NS
Q47: Talk about peritoneal dialysis	Older	1.06	0.58			NS	NS
Q48: Involved in choosing treatment	Young	2.07	−1.00			NS	NS
Q48: Involved in choosing treatment	Older	1.65	−1.14			NS	NS

Note: All the observed DIFs were non-significant at 0.05 level after multiple test adjustment

Young= Less than 65 years old, Older = More than 65 years old, DTF= Construct-level differential test functioning