Supplementary Material for: Electronic Patient-Reported Outcomes in Hidradenitis Suppurativa: Content Validity and Usability of the Electronic Hidradenitis Suppurativa Symptom Daily Diary, Hidradenitis Suppurativa Symptom Questionnaire and Hidradenitis Suppurativa Quality of Life Questionnaire

Background: Hidradenitis suppurativa (HS), a chronic skin condition that causes pain and physical dysfunction, can impact significantly on quality of life. Disease‑specific tools have been designed to assess the patient impact of HS, including the HS Symptom Daily Diary (HSSDD), the HS Symptom Questionnaire (HSSQ) and the HS Quality of Life (HiSQOL©) questionnaire, which have been developed into electronic instruments (eHSSDD, eHSSQ and eHiSQOL©). Objectives: To establish the content validity of the electronic version of the HSSDD and HSSQ, and the acceptability and usability of the HSSDD, HSSQ and HiSQOL© using concept elicitation and cognitive debriefing interviews. Methods: This was a non‑interventional qualitative video interview study involving participants aged ≥18 years with moderate to severe HS recruited from a single clinical site in the USA. Interviews gathered feedback on participants’ symptom experience, followed by training and completion of the eHSSDD, eHSSQ, and eHiSQOL© questionnaires on electronic hand-held devices. Participants were then interviewed on the content of the eHSSDD and eHSSQ, and the acceptability and usability of all three instruments. Interviews were transcribed and qualitatively analysed. Results: Twenty participants with moderate to severe HS (median age: 41.5 [range: 20.0–64.0]; n=16/20 female) were included. All participants found the eHSSDD, eHSSQ and eHiSQOL© instructions clear, and described the instruments as ‘easy’, ’simple’ and ’self-explanatory’. Overall understanding of individual items within the eHSSDD and eHSSQ was high; however, 6/20 participants had difficulty in understanding the ‘average skin pain’ item in the eHSSDD. All participants were able to accurately recall their symptoms within the recall periods of the eHSSDD and eHSSQ, although 4/20 participants found the 24-hour recall period of the eHSSDD limiting. Completion time was quick across all instruments and usability was high, with the majority of participants reporting no difficulty in completing questionnaires on electronic devices. Conclusion: The concepts covered in the eHSSDD and eHSSQ are relevant and important to patients, supporting their content validity. The findings also provide evidence of acceptability and usability of the eHSSDD, eHSSQ, and eHiSQOL©. A limitation was that all participants were recruited from a single site, which may have introduced selection bias and thus limit the generalisability of results.