International Hidradenitis Suppurativa Severity Score System
Physician-Reported Clinical Assessment
A validated dynamic scoring system for hidradenitis suppurativa that captures disease activity by counting three lesion types with weighted multipliers. Suitable for monitoring treatment response over time.
About the IHS4
Severity Bands
| Score Range | Classification | Interpretation |
|---|---|---|
| 0 – 3 | Mild | Mild hidradenitis suppurativa |
| 4 – 10 | Moderate | Moderate hidradenitis suppurativa |
| 11 – 1000 | Severe | Severe hidradenitis suppurativa |
Clinical Background
The IHS4 is a validated dynamic scoring system developed by the European Hidradenitis Suppurativa Foundation (EHSF) through a two-round Delphi consensus process and validated prospectively in 236 patients across 11 centres. Unlike the static Hurley classification, the IHS4 captures inflammatory disease activity at a specific point in time, making it suitable for monitoring treatment response.
The IHS4 requires counting three types of inflammatory lesions across all affected body areas: inflammatory nodules (round, palpable, greater than 1 cm), abscesses (fluctuant, pus-containing), and draining tunnels (tracts that intermittently or continuously discharge fluid). Only active, draining tunnels are counted; non-draining or inactive tunnels and scars are excluded. The formula is: IHS4 = (nodules x 1) + (abscesses x 2) + (draining tunnels x 4).
Current expert recommendation is to use both the Hurley classification and IHS4 in combination: Hurley for overall disease categorization and surgical planning, and IHS4 for visit-to-visit monitoring and clinical trial endpoints.
References
- Zouboulis CC, Tzellos T, Kyrgidis A, Jemec GBE, Bechara FG, Giamarellos-Bourboulis EJ, et al.. Development and validation of the International Hidradenitis Suppurativa Severity Score System (IHS4), a novel dynamic scoring system to assess HS severity. Br J Dermatol. 2017;177(5):1401-1409. doi:10.1111/bjd.15748
- Zouboulis CC, Prens EP, Sayed CJ, et al.. IHS4 as a holistic measure of HS disease severity compared with Hurley staging: a post hoc analysis of the SUNRISE and SUNSHINE phase 3 trials of secukinumab. J Eur Acad Dermatol Venereol. 2024;38(6):e496-e499. doi:10.1111/jdv.19681
- Thorlacius L, Garg A, Riis PT, et al.. Inter-rater agreement and reliability of outcome measurement instruments and staging systems used in hidradenitis suppurativa. Br J Dermatol. 2019;181(3):483-491. doi:10.1111/bjd.17716
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