The Psoriasis Area Severity Index (PASI) is a tool used to measure the severity of psoriasis, a chronic autoimmune skin condition characterized by red, scaly patches on the skin. PASI takes into account the extent of psoriatic involvement (area) as well as the severity of erythema (redness), induration (thickness), and desquamation (scaling) present within the involved regions. It provides a quantitative assessment of psoriasis severity and is commonly used in clinical trials and practice to monitor disease progression and treatment efficacy.
Microsoft Word – Psoriasis Area and Severity Index _PASI_ – 01.10.12 (huidziekten.nl)
Psoriasis Area Severity Index (PASI) Score
| Plaque characteristic | Lesion score | Head | Upper Limbs | Trunk | Lower Limbs |
| Erythema | 0 = None 1 = Slight 2 = Moderate 3 = Severe 4 = Very severe |
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| Induration/Thickness | |||||
| Scaling | |||||
| Add together each of the 3 scores for each body region to give 4 separate sums (A). | |||||
| Lesion Score Sum (A) | |||||
| Percentage area affected | Area score | Head | Upper Limbs | Trunk | Lower Limbs |
| Area Score (B) Degree of involvement as a percentage for each body region affected (score each region with score between 0-6) |
0 = None 1 = Slight 2 = Moderate 3 = Severe 4 = Very severe |
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| Multiply Lesion Score Sum (A) by Area Score (B), for each body region, to give 4 individual subtotals (C). | |||||
| Subtotals (C) | |||||
| Multiply each of the Subtotals (C) by amount of body surface area represented by that region, i.e. x 0.1 for head, x 0.2 for upper body, x 0.3 for trunk, and x 0.4 for lower limbs. | |||||
| Body Surface Area | x 0.1 | x 0.2 | x 0.3 | x 0.4 | |
| Totals (D) | |||||
| Add together each of the scores for each body region to give the final PASI Score. | |||||
| PASI Score | |||||
The PASI score ranges from 0 to 72, with higher scores indicating more severe psoriasis. Here’s a breakdown of the severity levels:
PASI score < 10: Mild psoriasis
PASI score 10-20: Moderate psoriasis
PASI score > 20: Severe psoriasis
References:
- El Miedany Y, El Gaafary M, Youssef S, Almedany S, Palmer D. Using Simulation in Clinical Education: Psoriasis Area and Severity Index (PASI) Score Assessment. Curr Rheumatol Rev. 2016;12(3):195-201. [Medline]
- Manchanda Y, De A, Das S, Chakraborty D. Disease Assessment in Psoriasis. Indian J Dermatol. 2023 May-Jun;68(3):278-281. [Medline]
- Robinson A, Kardos M, Kimball AB. Physician Global Assessment (PGA) and Psoriasis Area and Severity Index (PASI): why do both? A systematic analysis of randomized controlled trials of biologic agents for moderate to severe plaque psoriasis. J Am Acad Dermatol. 2012 Mar;66(3):369-75. [Medline]
Created Mar 25, 2024.
