How is the VASI score calculated?

How to Calculate the VASI Score

The VASI (Vitiligo Area Scoring Index) is calculated using a composite estimate that multiplies the percentage of body surface area affected by vitiligo in each anatomical region by the degree of depigmentation within those patches, with body regions divided according to the rule of nines. 1, 2

Core Calculation Method

The VASI quantifies vitiligo through two essential parameters that are multiplied together for each body region 2:

• Body surface area involvement: Assessed using the rule of nines to divide the body into anatomical regions (head/neck, trunk, upper extremities, lower extremities, hands, feet) 1
• Degree of depigmentation: Estimated as the percentage of depigmentation within the affected patches in each region 1, 3

The formula for each body region is: (% of body region affected) × (% depigmentation) = regional VASI score. 3

Scoring Range and Interpretation

• Facial VASI (F-VASI): Ranges from 0 to 3, with median baseline scores around 0.70 in clinical trials 4
• Total body VASI (T-VASI): Ranges from 0 to 100, with median baseline scores around 6.76 in clinical trials 4

Clinically Meaningful Change Thresholds

A 75% improvement in F-VASI and 50% improvement in T-VASI represent clinically meaningful treatment success, as these thresholds correlate with patient-reported improvement. 2

More granular thresholds based on recent psychometric validation 4:

• F-VASI: Improvement of 0.38-0.60 points represents clinically meaningful change
• T-VASI: Improvement of 1.69-3.88 points represents clinically meaningful change

Reliability Metrics

The VASI demonstrates robust psychometric properties when performed by trained raters 2, 5:

• Interobserver reliability: ICC 0.93 for VASI, indicating excellent agreement between different assessors 5
• Intraobserver reliability: ICC 0.93 for VASI, indicating excellent consistency when the same assessor repeats measurements 5
• Smallest detectable change (SDC): 7.1% for interobserver measurements and 4.7% for intraobserver measurements 2, 5

These SDC values mean that changes smaller than 7.1% between different observers or 4.7% by the same observer may represent measurement variability rather than true clinical change. 5

Validation Against Clinical Outcomes

The VASI correlates well with both physician and patient assessments 1, 3:

• Correlation with physician global assessment: P < 0.001 3
• Correlation with patient global assessment: P = 0.05 3
• Strong correlation with Patient Global Impression of Change (PaGIC-V): r = 0.610 for F-VASI and r = 0.512 for T-VASI 4

Critical Limitations to Consider

The VASI only accounts for the area and degree of depigmentation—it does not incorporate disease location, quality of life impact, or disease activity/progression. 1, 2

This is a significant clinical limitation because 1, 2:

• Vitiligo affecting visible areas (hands, face) has disproportionate psychosocial impact not captured by VASI scores
• Two patients with identical VASI scores may have vastly different quality of life depending on lesion location
• The VASI cannot distinguish between stable and actively spreading disease

Recommended Complementary Assessments

For comprehensive patient evaluation, combine VASI with quality of life measures (such as Skindex or DLQI), patient global assessments, and specific documentation of visible body area involvement. 1, 2

Alternative or complementary tools include 1, 2:

• Vitiligo European Task Force (VETF) assessment: Combines extent evaluation using rule of nines, disease staging based on cutaneous and hair pigmentation, and progression assessment using Wood's light examination
• Self-Assessment VASI (SAVASI): Validated patient-administered version with high correlation to physician-assessed VASI (ICC 0.97), useful for large studies and enhancing patient engagement 6

Practical Clinical Application

The VASI is most useful for establishing baseline disease severity, documenting disease progression over time, and quantifying treatment response in clinical trials. 2

When using VASI in practice 7, 5:

• Standardized training improves reliability from "moderate" to "good" or "excellent" for most raters
• F-VASI generally shows more variability than T-VASI, with intrarater reliability ranging from "poor" to "excellent" depending on the assessor
• Exercise caution when interpreting score changes in individual patients due to the relatively large SDC values