Scarletred®Vision, Hidradenitis Suppurativa


Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease affecting up to 2% of European adults. Disease activity is commonly assessed by counting of inflammatory nodules, abscesses and fistulas. Thus, it is time consuming and subject to inter-rater variability. We sought to assess HS disease activity by means of automated, digital image analyses. Digital images of axillary and inguinogenital HS were collected in a clinical routine setting, using smartphones and a CE medical device certified skin imaging platform. Photos were automatically normalized for illumination and color. Image characteristics such as an erythema-score and image complexity were calculated for all photos comparing affected and unaffected skin. Parameters were used to calculate the HS Activity and Severity Score (HiSASS) and correlated with the average Physician Global Assessment (PGA) of each picture provided by 3 independent dermatologists. Follow-up images were used to evaluate disease activity over time. 226 photos of 150 HS-affected skin areas (52% axillary, 48% inguinogenital) and 33 non-affected controls were analyzed. HiSASS correlated significantly with PGA scores (p=.000). Further, HiSASS clustered disease activity into three categories similar to the Hurley grading system: HiSASSave mild (PGA-0/1): 0.7-1.3, moderate (PGA-2/3): 1.5-1.6 and severe disease (PGA-4/5): 1.8-1.9. Additinoally, the HiSASS allowed for a dynamic assessment of disease activity over time: Increasing HiSASS in the follow-up group (n=30; baseline: HiSASSave=1.6, follow-up: HiSASSave=1.9) indicated disease worsening and correlated significantly with increasing PGA scores (p=.009). Normalized mobile phone images could allow a fast, reliable, dynamic and reproducible disease severity assessment in HS patients.

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