PASI Calculator for Psoriasis in All Skin Types
The Bright Med PASI calculator helps healthcare professionals score psoriasis severity using the Psoriasis Area and Severity Index. Unlike standard calculators, it includes Fitzpatrick skin type reference images, so erythema is less likely to be underestimated in darker skin. Enter scores for each body region and copy the result straight into your clinical notes.
How PASI is calculated
PASI scores four body regions: head and neck, upper limbs, trunk and lower limbs. In each region, erythema, induration and desquamation are scored from 0 to 4, and the area affected is scored from 0 to 6. The sum of the sign scores is multiplied by the area score and weighted by region: 0.1 for the head, 0.2 for the upper limbs, 0.3 for the trunk and 0.4 for the lower limbs. The total ranges from 0 to 72.
Interpreting the score
Most NICE technology appraisals for advanced therapies in plaque psoriasis define severe disease as a PASI of 10 or more with a DLQI of more than 10. Treatment response is measured against baseline:
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PASI 75: 75% reduction
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PASI 90: 90% reduction
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PASI 100: complete clearance
NICE defines an adequate response as PASI 75, or PASI 50 with a 5-point reduction in DLQI.
Assessing PASI in skin of color
In darker skin, inflammation often appears violaceous, dusky or hyperpigmented rather than red, so erythema is easily scored too low. This lowers the total PASI and can affect treatment eligibility. This calculator includes reference images for each Fitzpatrick skin type to help you grade erythema accurately. Assess induration and scaling by touch and close inspection, as these are less affected by skin tone.
Frequently asked questions
What PASI score counts as severe psoriasis?
A PASI of 10 or more with a DLQI of more than 10, under most NICE technology appraisals.
What does PASI 90 mean?
A reduction of at least 90% from baseline, meaning clear or almost clear skin.
Is PASI reliable in darker skin?
Yes, but erythema is often underestimated. Skin type–specific reference images improve consistency.
When should PASI be recorded?
At baseline, at the end of induction, and at each review.
Educational use only
This calculator is an educational tool for healthcare professionals. It is not a medical device and does not replace clinical judgement or local guidelines. Check eligibility against current NICE guidance and your local pathway.