ToolsCalculators
Psoriasis Area and Severity Index (PASI)
Composite severity and extent score for plaque psoriasis across 4 body regions.
Psoriasis Area and Severity Index (PASI)
Head - erythema
Head - induration
Head - desquamation
Head - area involved
Trunk - erythema
Trunk - induration
Trunk - desquamation
Trunk - area involved
Upper limbs - erythema
Upper limbs - induration
Upper limbs - desquamation
Upper limbs - area involved
Lower limbs - erythema
Lower limbs - induration
Lower limbs - desquamation
Lower limbs - area involved
ResultPASI 0.0
Mild psoriasis (PASI <10).
- Head contribution
- 0.0
- Trunk contribution
- 0.0
- Upper limb contribution
- 0.0
- Lower limb contribution
- 0.0
- Total PASI
- 0.0
When to use
- Quantifying plaque psoriasis severity and extent for treatment decisions and monitoring response to systemic/biologic therapy.
Formula
PASI = 0.1x(Ehead+Ihead+Dhead)xAhead + 0.2x(Earms+Iarms+Darms)xAarms + 0.3x(Etrunk+Itrunk+Dtrunk)xAtrunk + 0.4x(Elegs+Ilegs+Dlegs)xAlegs, where E/I/D (erythema, induration, desquamation) are each graded 0-4 and A (area) is graded 0-6 by % body surface area involved per region. Range 0-72.
Pearls and pitfalls
- PASI 75/90 (percentage improvement from baseline) is the standard trial endpoint, not the absolute score.
- Weighting (head 0.1, upper limbs 0.2, trunk 0.3, lower limbs 0.4) approximates each region's proportion of total body surface area.