Psoriasis Scalp Severity Index (PSSI)
DESCRIPTION:
The Psoriasis Scalp Severity Index scale, a modified equivalence to the PASI score, measures psoriasis severity of the scalp based on erythema, desquamation, and infiltration. The score ranges from 0 (no signs of psoriasis) to 72 (the most severe form of disease).1,2
DISEASE STATES:
Psoriasis
VALIDATED USES:
Treatment monitoring
ADMINISTRATION METHOD:
Clinician
COMMONLY USED IN:
Clinical trials, research
DETAILED DESCRIPTION:
The PSSI measures the severity of psoriasis of the scalp, a historically difficult-to-treat area.1-3 The PSSI is typically used exclusively in clinical trials.2,3 A physician or clinician examines the visibility of lesions, pruritus degree on psoriasis-affected skin, and severity of erythema, desquamation, and infiltration.1-4
PSSI = Sum of scores for desquamation (D), erythema (E), and induration (I) x percent of involved area (range 0–72):2,3
PSSI SCORING
| Severity Score | |
|---|---|
| 0 | None |
| 1 | Slight |
| 2 | Moderate |
| 3 | Severe |
| 4 | Very severe |
| Area of Involvement Score | |
|---|---|
| 0 | None |
| 1 | 1%–9% |
| 2 | 10%–29% |
| 3 | 30%–49% |
| 4 | 50%–69% |
| 5 | 70%–89% |
| 6 | 90%–100% |
| Plaque Characteristic | Plaque Score |
|---|---|
| Desquamation (D) | 0–4 |
| Erythema (E)+ | 0–4 |
| Induration (I)+ | 0–4 |
| Severity Score= | |
| Area Scorex | 0–6 |
| PSSI SCORE= | 0–72 |
VALIDITY:
Thaçi D et al. 2001 demonstrated good internal validity with sensitivity to detect change in the clinical trial setting.4
LIMITATIONS:
PSSI excludes the face and neck and may be cumbersome and time-consuming.2,4 Estimating area involvement can be difficult and can decrease interrater reliability.2 Not integrated into BSA, PGA, PASI. Disease severity may be attributed to percent of area involved and not plaque characteristics.4
This resource is intended for educational purposes only and is intended for US healthcare professionals. Healthcare professionals should use independent medical judgment. All decisions regarding patient care must be handled by a healthcare professional and be made based on the unique needs of each patient.
References: 1. Nicolescu AC, Ionescu MA, Constantin MM, et al. Psoriasis management challenges regarding difficult-to-treat areas: therapeutic decision and effectiveness. Life (Basel). 2022;12(12):2050. doi:10.3390/life12122050 2. Wechter T, Heath MS, Aung-Din D, Sahni DR, Cline A, Feldman SR. Current psoriasis efficacy outcome measures in clinical trials. Curr Dermatol Rep. 2018;7(2):261-268. doi:10.1007/s13671-018-0237-6 3. Frez ML, Asawanonda P, Gunasekara C, et al. Recommendations for a patient-centered approach to the assessment and treatment of scalp psoriasis: a consensus statement from the Asia Scalp Psoriasis Study Group. J Dermatolog Treat. 2014;25(1):38-45. doi:10.3109/09546634.2012.742176 4. Thaçi D, Daiber W, Boehncke WH, Kaufmann R. Calcipotriol solution for the treatment of scalp psoriasis: evaluation of efficacy, safety and acceptance in 3,396 patients. Dermatology. 2001;203(2):153-156. doi:10.1159/000051731
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