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DLQI
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mPASI
PASI Score
PASI (Psoriasis Area and Severity Index): The gold standard for measuring clinical severity and treatment response in chronic plaque psoriasis.
Head (10%)
Area Involvement (0-6)
0
1
2
3
4
5
6
erythema
0
1
2
3
4
induration
0
1
2
3
4
scaling
0
1
2
3
4
Trunk (30%)
Area Involvement (0-6)
0
1
2
3
4
5
6
erythema
0
1
2
3
4
induration
0
1
2
3
4
scaling
0
1
2
3
4
Upper Limbs (20%)
Area Involvement (0-6)
0
1
2
3
4
5
6
erythema
0
1
2
3
4
induration
0
1
2
3
4
scaling
0
1
2
3
4
Lower Limbs (40%)
Area Involvement (0-6)
0
1
2
3
4
5
6
erythema
0
1
2
3
4
induration
0
1
2
3
4
scaling
0
1
2
3
4
Compute Total PASI Score
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Gold standard for evaluating the severity and extent of psoriasis.
Determining eligibility for systemic and biologic therapies.
Tracking patient response to treatment (e.g., PASI 75 or PASI 90 response).
Section 2
Formula & Logic
Formula
PASI = 0.1(E_h + I_h + D_h)A_h + 0.2(E_u + I_u + D_u)A_u + 0.3(E_t + I_t + D_t)A_t + 0.4(E_l + I_l + D_l)A_l
Variables
E: Erythema, I: Induration (thickness), D: Desquamation (scaling). Each graded 0-4.
A: Area of involvement graded 0-6 (1=1-9%, 2=10-29%, 3=30-49%, 4=50-69%, 5=70-89%, 6=90-100%).
Subscripts: h=head/neck, u=upper limbs, t=trunk, l=lower limbs.
Section 3
Pearls/Pitfalls
Clinical Pearls
PASI is heavily skewed towards surface area. Small but highly severe plaques may yield a low score.
Max score is 72, but scores >40 are exceedingly rare in clinical practice.
PASI 75 means the patient has achieved a 75% reduction in their baseline PASI score.
Section 4
Next Steps
Severity Definitions
PASI < 5: Mild.
PASI 5-10: Moderate.
PASI > 10: Severe. Usually warrants systemic therapy.
Section 5
Evidence Appraisal
Last Comprehensive Review: 2026
Related Dermatology Tools
EASI Score
GAGS
HiSCR
IGA
IHS4
Lund-Browder Chart
Melanoma Risk Screening
mPASI
MSK Melanoma Nomogram
Parkland Formula
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