Table 3: Reliability testing of QOL-PCD scales:
Internal consistency measured by Cronbach’s α and test–retest reliability measured by intraclass correlation coefficients (ICC)
| QOL-PCD1scales | No. of Items | Mean (SD) of scales |
Cronbach’s α2 | ICC3 (95% CI) |
|---|---|---|---|---|
| Child QOL-PCD N=71 | N=13 | |||
| Physical functioning | 5 | 79.15 (20.03) | 0.76 | 0.540 (−0.507 to 0.806) |
| Emotional functioning | 4 | 72.65 (16.07) | 0.62 | 0.652 (−0.141 to 0.894) |
| Treatment Burden | 5 | 56.34 (24.06) | 0.66 | 0.895 (0.656 to 0.968) |
| Social functioning | 5 | 79.71 (19.47) | 0.61 | 0.890 (0.640 to 0.967) |
| Upper respiratory symptoms | 5 | 66.48 (22.51) | 0.76 | 0.807 (0.366 to 0.941) |
| Lower respiratory symptoms | 6 | 63.07 (17.54) | 0.70 | 0.791 (0.315 to 0.936) |
| Ears and hearing symptoms | 4 | 74.65 (18.97) | 0.60 | 0.841 (0.479 to 0.951) |
| Adolescents QOL-PCD N=85 | N=17 | |||
| Physical functioning | 5 | 80.95 (23.67) | 0.90 | 0.889 (0.692 to 0.960) |
| Emotional functioning | 4 | 73.82 (19.76) | 0.71 | 0.763 (0.321 to 0.917) |
| Treatment Burden | 3 | 70.82 (23.96) | 0.70 | 0.861 (0.586 to 0.953) |
| Role | 3 | 80.78 (19.58) | 0.71 | 0.842 (0.565 to 0.943) |
| Social Functioning | 4 | 62.35 (23.27) | 0.70 | 0.752 (0.314 to 0.910) |
| Vitality | 3 | 59.22 (21.64) | 0.76 | 0.859 (0.609 to 0.949) |
| Upper Respiratory Symptoms | 5 | 65.33 (18.54) | 0.70 | 0.734 (0.265 to 0.904) |
| Lower Respiratory Symptoms | 7 | 58.23 (17.33) | 0.82 | 0.716 (0.217 to 0.897) |
| Ears and Hearing | 4 | 82.64 (20.67) | 0.73 | 0.868 (0.623 to 0.954) |
| Parent Proxy N=68 | N=13 | |||
| Physical functioning | 5 | 79.21 (21.26) | 0.86 | 0.865 (0.557 to 0.959) |
| Emotional functioning | 3 | 68.95 (16.69) | 0.74 | 0.333 (−1.32 to 0.808) |
| Treatment Burden | 4 | 59.68 (24.46) | 0.78 | 0.607 (−0.286 to 0.880) |
| Social functioning | 3 | 79.24 (22.05) | 0.74 | 0.853 (0.519 to 0.955) |
| Health Perception | 4 | 66.79 (17.25) | 0.80 | 0.435 (−0.852 to 0.828) |
| Eating and weight | 3 | 72.88 (28.95) | 0.73 | 0.849 (0.505 to 0.954) |
| Upper respiratory symptoms | 4 | 55.39 (22.98) | 0.70 | 0.626 (−0.227 to 0.886) |
| Lower respiratory symptoms | 6 | 58.66 (19.44) | 0.84 | 0.645 (−0.162 to 0.892) |
| Ears and hearing symptoms | 3 | 75.49 (22.52) | 0.62 | 0.897 (0.662 to 0.969) |
1
PCD, primary ciliary dyskinesia; QOL, quality of life.
2
Cronbach’s α >0.70 indicates good internal consistency.
3
ICC (intra-class correlation coefficient) >0.60 indicates good stability and >0.75 excellent stability of the scales.