Comparison of clinical and sonographic scores in hidradenitis suppurativa and proposal of a novel ultrasound scoring system.

BACKGROUND Hidradenitis suppurativa (HS) is a chronic, inflammatory disease that presents with nodules, abscesses and fistulae affecting the apocrine gland-bearing skin. Since few years, ultrasonography is used to better characterize HS skin lesions but comparison between clinical and sonographic scores has been made only in small series of patients. The aim is to assess concordance between clinical and sonographic scores in a larger cohort of HS patients. METHODS We conducted a retrospective observational study on 140 HS patients comparing two clinical score systems, Hurley and HS-Physical Global Assessment (PGA), with two ultrasonographic scores, SOnographic Score of Hidradenitis Suppurativa (SOS-HS) and ultrasonographic HS-PGA, a novel ultrasound scoring system set up by our group. We used the weighted Cohen's Kappa statistic (k) to evaluate the agreement. RESULTS Agreement between Hurley staging and SOS-HS was found in 61.4% of patients (weighted kappa 0.477), while agreement between clinical and ultrasonography HS-PGA scores was found in 35% of patients (weighted kappa 0.278), both findings suggesting a substantial disagreement. CONCLUSIONS Our study demonstrated a relevant disagreement between clinical and ultrasonography scores. Ultrasonography discovered non-clinically evident HS lesions, notably fistulae. Taken together, the above findings may support the view, previously suggested in expert panel reports, on the higher sensitivity of ultrasonography compared to clinics in HS.