Supplementary Material for: Development of HiSQOL: A Hidradenitis Suppurativa-Specific Quality of Life Instrument

Background: Hidradenitis suppurativa (HS) is a chronic and painful skin disease. In addition, HS lesions may be associated with pus and odour, potentially leading to significant stigma and, consequently, greatly affected quality of life (QOL). QOL is a multidimensional construct, which can be measured in various ways. However, generic or dermatologic QOL measures may not capture changes in QOL particularly affected in HS. Accordingly, patients and experts included in the HIdradenitis SuppuraTiva cORe outcomes set International Collaboration (HISTORIC) agreed that future clinical HS trials should measure HS-specific QOL. Objectives: To develop an HS-specific QOL instrument (HiSQOL, Hidradenitis Suppurativa Quality of life). Method: The initial phases of the questionnaire development, described in this study, included item generation by patient interviews, development of a pilot questionnaire, questionnaire refinement, and pilot testing. Results: For item generation, 21 patients were interviewed individually or in focus groups. Analysis of the interviews identified 105 candidate items and, next, a pilot questionnaire was developed. Finally, item reduction and two rounds of pilot testing resulted in a 23-item questionnaire representing physical, psychological, and social QOL dimensions. Conclusions: We have comprehensively explored on HS’s possible effect on the QOL of the affected individuals and identified a 23-item HS-specific QOL questionnaire. The questionnaire proved to be feasible, acceptable, and comprehensible in the second round of pilot testing. With HiSQOL, researchers can measure HS-specific QOL in future clinical trials, potentially enabling them to discover more effective treatment options. It is envisaged, that after thorough validation in a trial setting, a streamlined version of HISQOL may also become available for clinical use in daily practice.