Three signs rated 0 to 4 and an area score 0 to 6 in each of four body regions, weighted and summed to a total from 0 to 72. PASI 75, 90 and 100 are the standard efficacy endpoints for plaque psoriasis.
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Area involved
PASILLAErythema
PASILLEInduration
PASILLIDesquamation
PASILLDAt a glance
In trials
When PASI 75 was established as the standard endpoint, a 75% improvement was a strong result. Modern biologic therapies often clear skin almost completely, so trials now report PASI 90 and PASI 100 as key endpoints and compare treatments on them. That puts more weight on accurate scoring at the low end of the scale, where one region scored differently can change the result.
Psoriasis trials usually pair PASI with a static Physician Global Assessment or Investigator Global Assessment as a co-primary endpoint, body surface area involvement, and the DLQI for quality of life. Record the components of each so they can be checked.
Because PASI is multiplicative, very small areas with mild signs can produce scores that are hard to rate consistently. Train assessors specifically on minimal disease, and keep the same assessor for a participant where possible.
PASI 75
81%
PASI 90
62%
PASI 100
34%
Calculation
| Component | Values |
|---|---|
| Head and neck weight | 0.1 |
| Upper limbs weight | 0.2 |
| Trunk weight | 0.3 |
| Lower limbs weight | 0.4 |
| Signs (each) | Erythema, induration, desquamation: 0 none to 4 very severe |
| Area score | 0 none, 1 under 10%, 2 10 to 29%, 3 30 to 49%, 4 50 to 69%, 5 70 to 89%, 6 90 to 100% |
Total PASI = sum over regions of (erythema + induration + desquamation) × area score × weight.
In Capture
Each region is a form section with an area dropdown and three sign ratings. Range checks stop out-of-scale values, every component exports as its own variable with labels, and source data verification can be switched on for the endpoint fields.
Changed by Data manager · reason: critical safety value added
Copy the template and enter a test assessment in the free sandbox.
Before go-live
Four area scores and twelve sign ratings.
sPGA or IGA form alongside PASI.
Including minimal disease.
Same assessor for a participant where possible.
PASI 75, 90, 100 and absolute PASI in the analysis plan.
Separate forms for scalp or nails if needed.
The proportion of participants reaching a PASI at or below a fixed value, such as 2 or less, regardless of their baseline score.
An improvement of at least 90% from baseline, increasingly used as a key endpoint for modern biologic therapies.
In each of four regions, three signs rated 0 to 4 are summed and multiplied by the area score (0 to 6) and a region weight. The four region scores are added for a total of 0 to 72.
An improvement of at least 75% from the baseline PASI.
Head 0.1, upper limbs 0.2, trunk 0.3 and lower limbs 0.4.
PASI is widely used in research without a licence fee.
No. Store every component so the total can be recalculated and verified.
Components are stored as coded values, and region scores and the total are derived in analysis.
Keep exploring
Every component coded and checked. Free sandbox.