PASI vs EASI vs SCORAD: Which Severity Score for Which Patient?
Three validated severity scores exist for inflammatory skin disease, and choosing the right one matters for treatment decisions, audit, and clinical trials. Here is how to pick and use each effectively.
Why Objective Scoring Matters in Dermatology
Inflammatory skin diseases — psoriasis, atopic dermatitis, and related conditions — are notoriously subjective in clinical description. "Moderate" means different things to different clinicians. Severity scores solve this problem by providing a reproducible, numeric measure that:
- Guides treatment escalation decisions (especially biologic therapy thresholds)
- Allows meaningful before/after comparisons
- Satisfies audit, insurance pre-authorisation, and clinical trial criteria
- Creates a defensible record if treatment decisions are questioned
The three tools you will encounter most frequently are PASI (Psoriasis Area and Severity Index), EASI (Eczema Area and Severity Index), and SCORAD (SCORing Atopic Dermatitis).
PASI — Psoriasis Area and Severity Index
Used for: Plaque psoriasis primarily. Also used in psoriatic arthritis assessments (skin component).
What it measures: Erythema, induration (plaque thickness), and desquamation (scaling) — each scored 0–4 in four body regions (head, trunk, upper extremities, lower extremities). The area affected in each region is scored 0–6. A weighting factor is applied per region.
Score range: 0–72 (though scores above 40 are rare)
Calculation:
PASI = 0.1(H_severity × H_area) + 0.3(T_severity × T_area) + 0.2(UE_severity × UE_area) + 0.4(LE_severity × LE_area)
Where severity = erythema + induration + desquamation for that region.
Clinical thresholds:
| Score | Severity |
|---|---|
| <3 | Mild |
| 3–10 | Moderate |
| >10 | Severe |
Key thresholds for biologics:
- PASI ≥10 + DLQI ≥10 = typically qualifies for biologic therapy (UK NICE, most international guidelines)
- PASI 75 = 75% reduction = primary endpoint in most psoriasis trials
Limitations: PASI underweights lesions in cosmetically sensitive areas (face, hands, genitalia). A patient with severe facial psoriasis may score low on PASI while being significantly affected.
EASI — Eczema Area and Severity Index
Used for: Atopic dermatitis (eczema) — both paediatric and adult.
What it measures: Four signs (erythema, oedema/papulation, excoriation, lichenification) scored 0–3 in four body regions. Area involvement scored 0–6 per region. Weighting applied per region.
Score range: 0–72
Clinical thresholds:
| Score | Severity |
|---|---|
| 0 | Clear |
| 0.1–1.0 | Almost clear |
| 1.1–7.0 | Mild |
| 7.1–21 | Moderate |
| 21.1–50 | Severe |
| >50 | Very severe |
Key threshold: EASI ≥16 typically required for dupilumab (Dupixent) initiation in many markets.
EASI-50, EASI-75, EASI-90: Like PASI, a 50/75/90% reduction from baseline is the standard trial endpoint language.
Advantages over SCORAD: Physician-rated only (no patient-reported component), making it more suitable for clinical trial primary endpoints where observer independence is required.
SCORAD — SCORing Atopic Dermatitis
Used for: Atopic dermatitis — particularly useful in clinical practice because it incorporates patient-reported symptoms.
What it measures: Three components:
- Extent (A) — percentage of body surface affected, calculated using the rule of nines, scored 0–100
- Intensity (B) — six signs scored 0–3 (erythema, oedema, oozing/crusts, excoriation, lichenification, dryness), max 18
- Subjective symptoms (C) — itch and sleep loss, each 0–10 on VAS, max 20
Formula: SCORAD = A/5 + 7B/2 + C
Score range: 0–103
Clinical thresholds:
| Score | Severity |
|---|---|
| <25 | Mild |
| 25–50 | Moderate |
| >50 | Severe |
Objective SCORAD: Drops the subjective component (C), giving A/5 + 7B/2. Useful when comparing across patients or for registry data.
Patient-Oriented SCORAD (PO-SCORAD): A validated self-administered version patients can complete at home — useful for remote monitoring.
Which Score to Choose?
| Situation | Recommended score |
|---|---|
| Psoriasis severity assessment | PASI |
| Biologic eligibility for psoriasis (adalimumab, secukinumab, ixekizumab) | PASI + DLQI |
| Atopic dermatitis with clinical trial enrolment | EASI |
| Atopic dermatitis in routine clinical practice | SCORAD |
| Biologic eligibility for atopic dermatitis (dupilumab) | EASI or IGA |
| Paediatric atopic dermatitis with symptom tracking | SCORAD (includes itch/sleep) |
| Remote patient monitoring | PO-SCORAD |
Tracking Scores in Clinit
Clinit's dermatology module includes built-in calculators for all three scores:
- Enter values by region with a guided step-by-step interface
- Results are automatically stored in the patient timeline with date and treatment context
- Trend graphs show score trajectory across visits — critical for demonstrating biologic response
- Pre-authorisation reports can export the score history in a format insurers accept
- Scores that fall in clinically significant ranges trigger review alerts
Consistent scoring from first visit builds the longitudinal dataset that justifies treatment escalation — and protects you if a payer challenges the decision.