Investigator Global Assessment: Standardized 5-point static scale for clinical trials.
Select Global Severity
Assessment Ready
Select the IGA level based on the overall clinical appearance of inflammatory and non-inflammatory lesions.
Guidelines & Evidence
Verified
Last Review: 2026-07-17
When to Use
When to Use
Global evaluation of Atopic Dermatitis (AD) or Acne Vulgaris severity in clinical practice and clinical trials.
Required by the FDA as a primary efficacy endpoint in phase III dermatological drug trials.
Quick bedside assessment of disease burden when complex scoring (like EASI) is too time-consuming.
How it Works
The 5-Point Scale (vIGA-AD Scale)
0 - Clear: No inflammatory signs of AD. No erythema or induration/papulation.
1 - Almost Clear: Barely perceptible erythema, barely perceptible induration/papulation.
2 - Mild: Slight but definite erythema, slight but definite induration/papulation.
3 - Moderate: Clearly perceptible erythema, clearly perceptible induration/papulation.
4 - Severe: Marked erythema, marked induration/papulation.
Clinical Pearls
Clinical Pearls
The IGA evaluates the overall severity of the disease at a given point in time, without factoring in the extent of body surface area (BSA) affected. A patient with a small but extremely inflamed patch will score high.
In clinical trials, "treatment success" is typically defined strictly as achieving an IGA score of 0 or 1, AND at least a 2-point reduction from baseline.
For acne, the criteria differ slightly (focusing on comedones, papules, pustules, and nodules), but the 0-4 scale structure remains identical to ensure FDA compliance.
Next Steps
Clinical Action
01
IGA 0-1: Maintenance therapy (e.g., emollients, proactive low-potency topical steroids/calcineurin inhibitors).
02
IGA 2-3: Escalate to mid/high-potency topical therapies or add targeted oral/topical antibiotics for acne.
03
IGA 4: Strongly consider systemic therapy (biologics, oral isotretinoin, systemic immunosuppressants).
The Evidence
Primary Reference
The Validated Investigator Global Assessment for Atopic Dermatitis (vIGA-AD): The development and reliability testing of a novel clinical outcome measurement instrument for the severity of atopic dermatitis.
Simpson E et al. • J Am Acad Dermatol.. 2020;83(3):839-846. Demonstrates strong reliability and establishes the vIGA-AD as a harmonized instrument for clinical trials.
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Origins & History
The Investigator Global Assessment (IGA) emerged as a regulatory requirement by the FDA to provide a simple, static snapshot of disease severity. The International Eczema Council (IEC) later developed the vIGA-AD™ to harmonize the disparate versions of IGA scales previously used across different clinical trials.
Last Comprehensive Review: 2026-07-17