Table 1.
Summary of key measurement properties of the weekly average of daily worst itch scores in paediatric patients with atopic dermatitis aged 6–11 years
| Measurement property | Phase 3 Study (R668-AD-1652) (N = 361) |
|
|---|---|---|
| Test–retest reliability | ICCa at prespecified timepoints [n] | |
| Week 15 (test) and Week 16 (retest) (n = 342) | 0.95 | |
| Baseline (test) and Week 2 (retest) for subgroup with no change in PGID (n = 117) | 0.76 | |
| Construct validity | Pearson correlation coefficient with weekly average of the daily worst itch at baseline, Week 16 | |
| SCORAD itch VAS (n = 361, 344) | 0.69*, 0.78* | |
| CDLQI itch item score (n = 361, 345) | 0.56*, 0.58* | |
| PGID (n = 361, 345) | 0.65*, 0.67* | |
| SCORAD objective score (n = 361, 344) | 0.24*, 0.48* | |
| EASI total score (n = 361, 345) | 0.22*, 0.47* | |
| IGA (n = 361, 345) | NC b, 0.46* | |
| Known-groups validity | Mean weekly daily worst itch scores per known group (ANOVA F-statistic; p-value) | |
| PGID (not itchy at all, a little itchy, medium itchy, pretty itchy, very itchy) | ||
| Baseline (n = 1, 11, 70, 139, 140) |
6.00, 5.75, 6.39, 7.63, 8.87 (67.61; p < 0.0001) |
|
| Week 16 (n = 30, 149, 85, 52, 29) | 1.39, 2.99, 5.42, 5.98, 7.73 (75.61; p < 0.0001) | |
| CDLQI bands (no effect, small, moderate, very large, extremely large effect) | ||
| Baseline (n = 2, 46, 91, 98, 124) |
5.21, 6.22, 6.47, 7.18, 8.26 (26.65; p < 0.0001) |
|
| Week 16 (n = 85, 147, 64, 23, 24) |
2.36, 4.02, 5.41, 6.63, 7.18 (39.66; p < 0.0001) |
|
| POEM bands (clear, mild, moderate, severe, very severe) | ||
| Baseline (n = 1, 5, 70, 186, 99) |
6.29, 5.77, 6.86, 7.74, 8.71 (22.87; p < 0.0001) |
|
| Week 16 (n = 65, 92, 96, 66, 25) |
2.06, 3.28, 4.69, 6.08, 7.71 (56.08; p < 0.0001) |
|
| Responsiveness | Change in weekly average of the daily worst itch score from baseline to Week 16: mean (SD), median (n = 345) | −3.49 (2.60), −3.45 |
| Effect size of change from baseline to Week 16 (SD at baseline units) | −2.32 | |
| Standardised response mean (SD of change units) | −1.34 | |
| Pearson correlation coefficient with weekly average of the daily worst itch change from baseline to Week 16 | ||
| SCORAD itch VAS (n = 344) | 0.70* | |
| CDLQI itch score (n = 345) | 0.45* | |
| PGID (n = 345) | 0.58* | |
| PGIC (n = 345) | 0.50* | |
| SCORAD objective score (n = 344) | 0.46* | |
| EASI total score (n = 345) | 0.41* | |
| IGA (n = 345) | 0.40* | |
| Mean change in weekly average of the daily worst itch score by change in PGID subgroups (ANOVA F-statistic; p-value) | ||
| Improved, stable, worsened (n = 265, 61, 19) |
−4.09, −1.55, −1.35 (37.10; p < 0.0001) |
|
| Effect sizes of change: improved vs stable, improved versus worsened, stable versus worsened | 1.70, 1.82, 0.13 | |
Negative change scores denote improvement on the Worst Itch Scale
ANOVA analysis of variance, CDLQI Children’s Dermatology Life Quality Index, EASI Eczema Area and Severity Index, ICC intraclass correlation coefficient, IGA Investigator’s Global Assessment, NC not computed, PGIC Patient Global Impression of Change, PGID Patient Global Impression of Disease, POEM Patient-Oriented Eczema Measure, SCORAD SCORing Atopic Dermatitis, SD standard deviation, VAS visual analogue scale
*p < 0.01, Pearson correlation coefficients
aTwo-way mixed-effects ANOVA with absolute agreement for single measures was used to compute test–retest reliability ICCs [21]
bCorrelational analysis was not appropriate due to the baseline requirement (i.e. IGA = 4)