Background
Materials and methods
Study design and participants
Ethics
Survey
CFQ-R
EQ-5D
Demographic/clinical background form
Analysis
Model development and specifications
-
Model 1: All CFQ-R domains excluding the health domain
-
Model 2: CFQ-R domains that are statistically significant at the 10% level
-
Model 3: Model 2 + statistically significant squared terms
-
Model 4: Model 3 + interaction terms
-
Model 5: All CFQ-R items excluding the health domain items
-
Model 6: CFQ-R items that are statistically significant at the 10% level
-
Model 7: Model 6 with collapsed unordered items
-
Model 8: Best fitting model + gender and age
Model validation and comparison
Results
Sample characteristics
Characteristic
|
Statistic
| |
---|---|---|
N
| 401 | |
Age
| Mean ± SD | 28.7 ± 8.88 |
Range (min, max) | 18 - 62 | |
Sex
| Male: N (%) | 156 (38.9) |
Ethnicity (N %)
| White | 393 (98.0) |
Other | 8 (2.0) | |
Working/studying
| Yes: N (%) | 248 (49.4) |
Diagnosis of CF (years)
| Mean ± SD | 25.3 ± 9.1 |
Median | 25.0 | |
Range (min, max) | 1 - 59 | |
Recent FEV
1
Predicted
| Mean ± SD | 65.7 ± 27.3 |
Median | 67.0 | |
Range (min, max) | 17 - 99 | |
Last FEV
1
: N (%)
| 0 – 1 month | 242 (63.9) |
>1 - 3 months | 97 (25.6) | |
>3 months | 11 (2.9) | |
Recent Exacerbation: N (%)
| Yes | 114 (30.1) |
Requiring Hospitalisation
| N (%) of above | 42 (36.8) |
Descriptive statistics for EQ-5D and CFQ-R
Mild FEV
1
|
Moderate FEV
1
|
Severe FEV
1
|
Total sample
| |
---|---|---|---|---|
Mean ± SD
|
Mean ± SD
|
Mean ± SD
|
Mean ± SD
| |
EQ-5D
| ||||
Utility value
| 0.74 ± 0.27 | 0.70 ± 0.26 | 0.54 ± 0.29 | 0.67 ± 0.28 |
CFQ-R
| ||||
Physical functioning
| 67.18 ± 28.82 | 44.74 ± 26.01 | 20.63 ± 18.24 | 45.71 ± 30.83 |
Role functioning
| 71.83 ± 25.25 | 60.17 ± 24.00 | 41.87 ± 26.19 | 59.87 ± 27.54 |
Vitality
| 47.78 ± 23.06 | 41.09 ± 20.78 | 31.73 ± 17.68 | 40.69 ± 21.74 |
Emotional functioning
| 62.54 ± 25.49 | 57.89 ± 22.47 | 49.64 ± 19.82 | 57.47 ± 23.44 |
Social functioning
| 61.06 ±17.84 | 55.06 ± 19.26 | 50.94 ± 20.51 | 56.12 ± 19.35 |
Body image
| 64.23 ± 28.07 | 61.84 ± 27.27 | 43.91 ± 29.75 | 58.38 ± 28.96 |
Eating disturbance
| 77.35 ± 25.22 | 76.32 ± 25.33 | 65.73 ± 28.89 | 74.70 ± 26.28 |
Treatment burden
| 56.30 ± 23.68 | 44.83 ± 23.87 | 42.17 ± 22.61 | 49.40 ± 25.2 |
Health perceptions
| 58.94 ± 26.43 | 43.45 ± 21.23 | 24.90 ± 22.66 | 44.25 ± 26.16 |
Weight
| 69.52 ± 36.43 | 63.91 ± 39.77 | 42.17 ± 40.35 | 60.76 ± 40.29 |
Respiratory symptoms
| 61.00 ± 24.68 | 47.82 ± 21.48 | 38.55 ± 21.8 | 49.63 ± 24.44 |
Digestive symptoms
| 67.30 ± 24.65 | 71.80 ± 25.63 | 73.49 ± 22.00 | 71.27 ± 23.92 |
Regression modelling
Observed EQ-5D
|
OLS models
|
Tobit models
|
TPM models
| ||||
---|---|---|---|---|---|---|---|
Domain (3)
|
Item (5)
|
Domain (3)
|
Item (5)
|
Domain (3)
|
Item (8)
| ||
Mean
| 0.671 | 0.671 | 0.671 | 0.672 | 0.672 | 0.691 | 0.679 |
SD
| 0.282 | 0.223 | 0.245 | 0.225 | 0.250 | 0.236 | 0.254 |
Range of values
| - 0.349 - 1 | - 0.099 - 1.04 | - 0.165 - 1.183 | - 0.053 - 0.985 | - 0.167 - 1 | - 0.221 - 0.985 | - 0.200 - 1 |
ICC
| 0.715 | 0.801 | 0.716 | 0.811 | 0.717 | 0.820 | |
RMSE
| - | 0.127 | 0.111 | 0.173 | 0.136 | 0.127 | 0.096 |
MSE
| - | 0.030 | 0.029 | 0.030 | 0.018 | 0.029 | 0.017 |
BIC
| - | −214 | 383 | 45 | 626 | 256, − 201 | 574, 379 |
AIC
| - | −254 | −173 | 5 | 71 | 240, − 247 | 270, − 150 |
Observed EQ-5D range
|
N
|
Observed EQ-5D
|
OLS models
|
Tobit models
|
TPM models
| |||
---|---|---|---|---|---|---|---|---|
Domain (3)
|
Item (5)
|
Domain (3)
|
Item (5)
|
Domain (3)
|
Item (8)
| |||
−0.349 - 0.099
| 23 | −0.028 | 0.294 (0.321) | 0.197 (0.225) | 0.293 (0.320) | 0.185 (0.214) | 0.274 (0.307) | 0.160 (0.196) |
0.1 - 0.299
| 41 | 0.227 | 0.420 (0.211) | 0.337 (0.149) | 0.421 (0.209) | 0.335 (0.148) | 0.418 (0.214) | 0.320 (0.134) |
0.3 - 0.599
| 38 | 0.511 | 0.505 (0.130) | 0.518 (0.106) | 0.502 (0.136) | 0.517 (0.113) | 0.524 (0.135) | 0.532 (0.100) |
0.6 - 0.699
| 92 | 0.660 | 0.620 (0.106) | 0.643 (0.093) | 0.621 (0.110) | 0.643 (0.098) | 0.649 (0.115) | 0.655 (0.092) |
0.7 - 0.799
| 71 | 0.756 | 0.747 (0.084) | 0.736 (0.088) | 0.749 (0.093) | 0.737 (0.097) | 0.778 (0.099) | 0.761 (0.089) |
0.8 - 0.899
| 59 | 0.841 | 0.794 (0.109) | 0.804 (0.097) | 0.792 (0.103) | 0.804 (0.100) | 0.817 (0.101) | 0.816 (0.099) |
0.9 - 1
| 77 | 1 | 0.895 (0.107) | 0.938 (0.088) | 0.900 (0.100) | 0.949 (0.051) | 0.916 (0.084) | 0.948 (0.052) |
ANOVA | F = 107.30 | F = 176.10 | F = 105.70 | F = 183.84 | F =104.81 | F = 202.73 | ||
p < 0.001 |
p < 0.001 |
p < 0.001 |
p < 0.001 |
p < 0.001 |
p < 0.001 | |||
FEV
1
| ||||||||
Severe < 41%
| 92 | 0.552 | 0.550 (0.157) | 0.548 (0.132) | 0.548 (0.158) | 0.550 (0.133) | 0.565 (0.157) | 0.561 (0.121) |
Moderate 41-70%
| 136 | 0.695 | 0.684 (0.119) | 0.694 (0.107) | 0.683 (0.120) | 0.693 (0.101) | 0.703 (0.120) | 0.702 (0.099) |
Mild > 70%
| 105 | 0.741 | 0.755 (0.113) | 0.748 (0.097) | 0.760 (0.116) | 0.751 (0.090) | 0.781 (0.111) | 0.757 (0.076) |
ANOVA | F = 24.38 | F = 19.29 | 25.39 | F = 18.43 | F = 23.83 | F = 16.76 | ||
p< 0.001 |
p< 0.001 |
p < 0.001 |
p < 0.001 |
p < 0.001 |
p < 0.001 |
EQ-5D
|
OLS model 3
|
OLS model 5
|
Tobit model 3
|
Tobit model 5
|
TPM model 3
|
TPM model 5
| |
---|---|---|---|---|---|---|---|
Sample 1
| |||||||
N
| 97 | 97 | 97 | 97 | 97 | 97 | 97 |
Mean (SD)
| 0.6776 (0.277) | 0.6755 (0.205) | 0.6976 (0.252) | 0.6717 (0.207) | 0.6891 (0.238) | 0.6932 (0.214) | 0.6811 (0.270) |
Range
| −0.3490 - 1 | 0.2702 - 1.028 | 0.1038 - 1.269 | 0.2539 - 0.9729 | 0.1444 - 1 | 0.1814 - 0.9734 | 0.0133, 1 |
RMSE
| 0.141 | 0.163 | 0.160 | 0.160 | 0.187 | 0.187 | |
ICC
| 0.65 | 0.54 | 0.65 | 0.53 | 0.64 | 0.40 | |
Sample 2
| |||||||
N
| 101 | 101 | 101 | 101 | 101 | 101 | 101 |
Mean (SD)
| 0.6632 (0.288) | 0.6701 (0.243) | 0.6744 (0.297) | 0.6683 (0.246) | 0.6744 (0.297) | 0.6868 (0.263) | 0.6785 (0.329) |
Range
| −0.1810 - 1 | −0.0399 - 1.006 | −0.1850 - 1.242 | −0.0040 - 0.981 | −0.2001 - 1 | −0.1830 - 0.9838 | −0.1642, 1 |
RMSE
| 0.118 | 0.165 | 0.162 | 0.162 | 0.182 | 0.182 | |
ICC
| 0.79 | 0.61 | 0.79 | 0.64 | 0.79 | 0.50 | |
Sample 3
| |||||||
N
| 100 | 100 | 100 | 100 | 100 | 100 | 98 |
Mean (SD)
| 0.6742 (0.277) | 0.6696 (0.202) | 0.6791 (0.221) | 0.6779 (0.210) | 0.6808 (0.236) | 0.6954 (0.214) | 0.6886 (0.252) |
Range
| −0.1810 - 1 | 0.2417 - 0.9782 | 0.0777 - 1.193 | 0.2592 - 0.9824 | −0.0555 - 1 | 0.2593 - 0.9837 | 0.1442, 1 |
RMSE
| 0.146 | 0.196 | 0.204 | 0.204 | 0.223 | 0.223 | |
ICC
| 0.50 | 0.31 | 0.52 | 0.29 | 0.49 | 0.29 | |
Sample 4
| |||||||
N
| 103 | 103 | 103 | 103 | 103 | 103 | 103 |
Mean (SD)
| 0.6688 (0.287) | 0.6703 (0.238) | 0.6515 (0.281) | 0.6703 (0.237) | 0.6526 (0.302) | 0.6887 (0.248) | 0.6678 (0.295) |
Range
| −0.3310 - 1 | −0.0577 - 1.048 | −0.2275 - 1.201 | −0.0441 - 0.9839 | −0.2964 - 1 | −0.1583 - 0.9879 | −0.1745, 1 |
RMSE
| 0.120 | 0.185 | 0.180 | 0.180 | 0.207 | 0.207 | |
ICC
| 0.80 | 0.51 | 0.81 | 0.56 | 0.81 | 0.47 |
OLS Model 3
|
TPM Model 3
| |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Part 1
|
Part 2
| |||||||||||
Variable
|
Coefficient
|
Bootstrapped SE
|
95% Bootstrapped SE (Bias-corrected)
|
95% Bootstrapped SE (Bias-corrected)
|
95% Bootstrapped SE (Bias-corrected)
| |||||||
Physical
| 0.00651*** | (0.00141) | 0.0037 | 0.0091 | 0.02836*** | (0.00834) | 0.0113 | 0.0449 | 0.00615*** | (0.00188) | 0.0027 | 0.0101 |
Role
| 0.00287*** | (0.00057) | 0.0017 | 0.0040 | 0.03285*** | (0.01221) | 0.0114 | 0.0583 | 0.00336*** | (0.00075) | 0.0019 | 0.0048 |
Emotion
| 0.00693*** | (0.00211) | 0.0028 | 0.0110 | 0.04287*** | (0.01020) | 0.0247 | 0.0637 | 0.00821*** | (0.00277) | 0.0029 | 0.0134 |
Vitality
| 0.00127** | (0.00062) | 0.0001 | 0.0025 | 0.00592** | (0.00257) | 0.0009 | 0.0112 | ||||
Eat
| 0.00154*** | (0.00053) | 0.0005 | 0.0026 | 0.00206*** | (0.00067) | 0.0008 | 0.0034 | ||||
Weight
| −0.00058** | (0.00028) | −0.0011 | −0.00003 | −0.00090** | (0.00040) | −0.0017 | −0.0001 | ||||
Digest
| 0.00094** | (0.00044) | 0.0001 | 0.0018 | 0.00106* | (0.00061) | −0.0001 | 0.0023 | ||||
Physical squared
| −0.00004*** | (0.00001) | −0.0001 | −0.00002 | −0.00004** | (0.00002) | −0.0001 | −0.00001 | ||||
Vitality squared
| - | - | - | - | −0.00005* | (0.00003) | −0.0001 | 0.000003 | ||||
Emotions squared
| −0.00004*** | (0.00002) | −0.0001 | −0.00001 | −0.00006** | (0.00003) | −0.0001 | −0.00001 | ||||
Constant
| −0.09898 | (0.06297) | −0.2178 | 0.0296 | −0.22122*** | (0.07169) | −0.3604 | −0.0790 |