A growing family of outcome measurement proposals for hidradenitis suppurativa
Authors: L. Emtestam, J. Lapins, K. Sartorius
Journal: British Journal of Dermatology (2021)

Linked Article: Goldfarb et al. Br J Dermatol 2021; 184:905–912. Hidradenitis suppurativa (HS) seems to originate within the hair follicle infundibulum. Occlusion is followed by inflammation and development of the disease. For treatment, surgery is the gold standard,1 but it is not always practical, and in randomized controlled trials (RCTs), an anti-tumour necrosis factor-α agent was promising for HS.2 Genetics and other factors, such as smoking, microbes and adiposity, contribute to the disease phenotype, which includes boils, noduli, scars, secreting or nonsecreting fistulae (‘tunnels’), and inflammation mainly of inverse areas.3 It is of outmost importance to monitor disease activity over time, for both the clinician and the researcher. Carefully designed outcome measurement instruments and staging systems provide functioning benchmark tools for assessment of primary and secondary outcomes of interventional trials and to guide treatment selection properly. A motley clinical picture of HS has complicated the search for uniform outcome variables, and work has been ongoing for at least two decades. The classic Hurley clinical grading system4 has three stages: one or more abscesses with no sinus tract or cicatrization (stage I), one or more widely separated recurrent abscesses, with a tract and scarring (stage II), and the most severe cases, with multiple interconnected tracts and abscesses throughout an entire affected area (stage III). The Hurley grading system is useful for overall classification of cases and may form the basis for selection of appropriate treatment in selected anatomical regions, but it is not sufficiently dynamic in RCTs to compare treatment effects. A plethora of scores have been devised but not fully validated, and a few will be discussed here. In this issue of the BJD, Goldfarb et al.5 describe the Hidradenitis Area and Severity Index Revised (HASI-R), a new method inspired by the old Psoriasis Area and Severity Index. Their aim is to minimize time-consuming lesion counts, to estimate the body surface area of involved skin at predetermined anatomical regions, and to incorporate the signs of HS inflammation (erythema, thickness, drainage and tenderness). The original HASI and Severity and Area Score for Hidradenitis (SASH) instruments were merged into HASI-R with the addition of tunnel counting. SASH included inflammatory colour change, induration and the amount of open skin surface with an estimate of involved body surface area. During the rating session the outcome measurement systems mentioned in this commentary were included for comparison. According to Goldfarb et al. HASI-R had better interrater reliability than the other HS physical sign outcome measures. Furthermore, HASI-R had the highest intrarater reliability and good construct validity, and showed known-groups validity. The HASI-R was also the most preferred tool by the raters during the session. We all look forward to clever studies like the one from Goldfarb et al., and prospective clinical trials using HASI-R in order to find its place in the growing family of outcome measurements proposed for HS. In collaboration with Professor Gregor Jemec, all three authors of this commentary proposed a system for severity scoring, in which involved anatomical preselected regions are counted, and both inflammatory and noninflammatory lesions are classified and weighted according to type. Extra points are given for the longest distance between two lesions within each anatomical region and for regions containing Hurley stage III. The points are added to give an overall severity score.6 Later this system was modified.7 The HS-Physician Global Assessment (HS-PGA) is a simple objective total count, an anchored six-point PGA based on lesion counts in predilection areas.8 Hidradenitis Suppurativa Severity Score System (HS4) and International HS4 are two versions of a proposal for scoring developed through ambitious Delphi voting procedures involving more than 40 participants with special interest and expertise in HS, from all over the world.9 Nodules, abscesses and draining fistulas (‘tunnels’) are counted and weighted according to type. Hidradenitis Suppurativa Clinical Response (HiSCR), meant for RCTs, but not allowing direct comparisons between different centres, is another approach.2 HiSCR is a lesion count, designed retrospectively on the basis of results from a phase II clinical trial with adalimumab. In a recent publication, nine common outcome measurement instruments showed very wide intervals for agreement even among experienced raters.10 Much work is needed to reach consensus on how to measure the physical signs of HS. At the moment we would like to recommend the clinician to use the PGA, perhaps in combination with a visual analogue scale of the most troublesome region and the Dermatology Life Quality Index. Finally, ask the patient about the number of boils (or exacerbations) during the latest month. Lennart Emtestam: Conceptualization (equal); Data curation (equal); Formal analysis (equal); Funding acquisition (equal); Investigation (equal); Methodology (equal); Project administration (equal); Resources (equal); Software (equal); Supervision (equal); Validation (equal); Visualization (equal); Writing-original draft (equal); Writing-review & editing (equal). Jan Lapins: Conceptualization (equal); Data curation (equal); Formal analysis (equal); Funding acquisition (equal); Investigation (equal); Methodology (equal); Project administration (equal); Resources (equal); Software (equal); Supervision (equal); Validation (equal); Visualization (equal); Writing-original draft (equal); Writing-review & editing (equal). Karin Sartorius: Conceptualization (equal); Data curation (equal); Formal analysis (equal); Funding acquisition (equal); Investigation (equal); Methodology (equal); Project administration (equal); Resources (equal); Software (equal); Supervision (equal); Validation (equal); Visualization (equal); Writing-original draft (equal); Writing-review & editing (equal).