Why carry out this study?
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To develop a fit-for-purpose (well-designed, reliable and valid) scale to assess itch intensity in clinical trial settings for children aged 6–11 years. |
To provide a responder definition to identify children with a meaningful change in itch. |
What was learned from the study?
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The Worst Itch Scale is a well-defined, reliable, sensitive and valid scale for evaluating worst itch intensity in children aged 6–11 years with severe AD. |
The most appropriate within-patient threshold for defining a clinically relevant response was a ≥ 3–4-point change on the Worst Itch Scale score. |
Digital Features
Introduction
Methods
Development and Content Validation of Worst Itch Scale
Psychometric Evaluation of Worst Itch Scale
Measurement property | Phase 3 Study (R668-AD-1652) (N = 361) | |
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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 |
Establishing a Clinically Meaningful Within-Patient Change Threshold for Worst Itch Scale
Results
Development and Content Validation of Worst Itch Scale
Psychometric Evaluation of Worst Itch Scale
Patient Characteristics
Test–Retest Reliability
Construct Validity
Known-Groups Validity
Sensitivity to Change
Clinically Meaningful Within-Patient Change Threshold
Method | Change in Weekly Average of the Daily Worst Itch Scores from Baseline to Week 16 (N = 361) | |
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Mean | Median | |
Anchor-based | ||
PGID improvement of 1 point (n = 94) | −2.84 | −2.83 |
Supportive anchor-based | ||
PGIC improvement | ||
A little better (n = 85) | −2.43 | −2.08 |
Much better (n = 221) | −4.49 | −4.83 |
EASI response | ||
EASI 50–74 (n = 71) | −3.00 | −3.00 |
EASI 75–89 (n = 105) | −3.79 | −3.83 |
EASI 90–100 (n = 98) | −4.80 | −5.31 |
IGA response | ||
IGA 0 or 1 (n = 92) | −4.71 | −5.21 |
IGA improvement of ≥ 2 points (n = 215) | −4.22 | −4.29 |
Distribution-based | ||
One-half SD at baseline | 0.75 | |
SEMa | 0.34 to 0.74 |