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Psychometric Evaluation of the Facial and Total Vitiligo Area Scoring Index Instruments in the TRuE-V Phase 3 Studies
Kristen Bibeau1, Kathleen Butler1, Mingyue Wang1
1Incyte Corporation, Wilmington, DE, USA.
Introduction:
This study reports psychometric testing of the facial and total Vitiligo Area Scoring Index quantitative clinical instruments (F-VASI [range: 0-3], T-VASI [range: 0-100], respectively) using data from two phase 3 randomized, vehicle-controlled studies of ruxolitinib cream (TRuE-V1/TRuE-V2), the largest vitiligo trials conducted to date. Because VASI assessment is required by regulatory authorities, we evaluated the psychometric properties of the VASI instruments and confirmed thresholds for clinically meaningful change.
Methods:
The TRuE-V1/TRuE-V2 full analysis set population included 652 patients (≥ 12 years old with nonsegmental vitiligo affecting ≤ 10% total body surface area, F-VASI ≥ 0.5, and T-VASI ≥ 3 at baseline). Data collected using the facial and total Patient Global Impression of Change-Vitiligo (PaGIC-V) and Physician's Global Vitiligo Assessment (PhGVA) scales were used as anchors to assess F-VASI and T-VASI for reliability, validity, sensitivity to change, and clinically meaningful change.
Results:
Median F-VASI and T-VASI scores were 0.70 and 6.76, respectively, at baseline, decreasing to 0.48 and 4.80 at week 24. Test-retest reliability was excellent between screening and baseline for F-VASI (intraclass correlation coefficient [ICC]: 0.943) and T-VASI (ICC: 0.945). Among stable patients per PaGIC-V and PhGVA, reliability was moderate to good for both F-VASI (ICC: 0.891 and 0.739, respectively) and T-VASI (ICC: 0.768 and 0.686). F-VASI and T-VASI differentiated well among PhGVA categories mild/moderate/severe at baseline and week 24. Both VASI instruments detected changes assessed by correlations with PaGIC-V scores at week 24 (F-VASI, r = 0.610; T-VASI, r = 0.512) and changes in PhGVA scores from baseline to week 24 (F-VASI, r = 0.501; T-VASI, r = 0.344). Thresholds for clinically meaningful improvement per PaGIC-V and PhGVA were 0.38-0.60 for F-VASI and 1.69-3.88 for T-VASI.
Conclusions:
Data from the TRuE-V1/TRuE-V2 studies confirmed that F-VASI and T-VASI are reliable, valid, and responsive to change, with defined clinically meaningful change from baseline in patients with nonsegmental vitiligo.
Trial Registration:
The original studies were registered at ClinicalTrials.gov: NCT04052425/NCT04057573.
