Estimating individual health-related quality of life changes in low back pain patients

Table 3 Coefficient of Repeatability (CR) using different reliability and standard deviation estimates

PROMIS-29 Scale	SD₁ (n = 316)	SD_1* (n = 119)	SD₂ (n = 316)	SD_2* (n = 119)	SD₃	CR₁	CR₂	CR₃	CR₄	CR₅	CR₆
Physical function	7.12	7.19	7.85	5.36	3.92	6.30	6.36	11.28	7.70	10.87	7.43
Pain interference	7.32	7.25	9.03	6.35	4.74	5.13	5.08	15.54	10.93	13.13	8.80
Pain intensity	7.86	8.63	9.59	6.59	4.64	12.30	13.50	15.00	10.31	12.86	9.13
Fatigue	9.53	8.76	9.14	8.57	6.06	6.73	6.19	15.63	14.65	16.79	11.88
Sleep disturbance	7.43	7.07	7.03	5.90	4.21	8.73	8.31	10.56	8.86	11.65	8.18
Depression	6.72	6.42	6.00	5.61	4.07	6.15	5.87	9.50	8.89	11.28	7.78
Anxiety	8.69	8.60	8.23	7.61	5.36	8.34	8.25	12.90	12.86	14.86	10.55
Satisfaction with participation in social roles	8.83	8.04	9.97	7.92	5.58	4.64	4.23	18.48	14.68	15.45	10.98
Pain composite	6.61	6.85	8.50	5.39	3.88	6.50	6.74	13.32	8.45	10.75	7.47
Emotional distress	6.95	6.89	6.28	5.73	4.06	5.09	5.05	9.46	8.64	11.24	7.94
Physical health summary	7.30	7.25	8.12	5.23	3.82	5.57	5.54	11.18	7.20	10.57	7.25
Mental health summary	6.82	6.29	6.72	4.93	3.48	3.33	5.07	9.45	6.94	9.65	6.83

All scale scores were estimated using existing calibrations (T-score metric: mean = 50, SD = 10 in U.S. general population)
SD₁ SD baseline for the usual medical care group, SD_1* SD baseline for subgroup of usual medical care group reporting “about the same” on retrospective change item, SD₂ SD change for usual medical care group, SD_2* SD change for subgroup of usual medical care group reporting “about the same”, SD₃ SD within (MS_error * 2.77) for subgroup reporting “about the same”, CR₁ coefficient of repeatability (CR) based on internal consistency reliability and SD₁, CR₂ coefficient of repeatability (CR) based on internal consistency reliability and SD_1*, CR₃ CR based on random effects test–retest intraclass correlation and SD₂, CR₄ CR based on random effects test–retest intraclass correlation and SD_2*, CR₅ CR based on SD₃, CR₆ CR based on 1.96 * SD_2* /\(\sqrt{2 }\)

ISSN: 1471-2474