DEAR EDITOR, Hidradenitis suppurativa (HS) is an inflammatory skin disease described as chronic and recurrent, with intermittent periods of worsening, also described as ‘flares’. 1–3 The core domain set for HS trials is being developed and calls for the assessment of flare frequency and duration. 4 Yet a recent literature review demonstrated that there are few precise definitions of HS flare. 5 Notably, it is the person with HS who experiences flare and there is little data pertaining to the lived experience of people with HS to inform flare definition. The aim of this study was to explore the patient perspective of HS flare.

A qualitative study was conducted that utilized in-depth semistructured interviews and focus groups. Participants were recruited from a research network of four academic health systems in the mid-Atlantic USA The inclusion crtieria were HS for at least 3 months, active lesions in the prior 12 months and age≥ 18 years. Candidates were excluded if they were not fluent in English or had mental impairment that would interfere with responses. Participants were purposively selected to ensure a mixture of HS stage, sex and race. Semistructured interviews and focus groups were conducted between January and March 2018 by one of us (JSK) using a topic guide designed to explore the participants’ experiences with flares. Participants were asked open-ended questions, with more focused questions to explore their responses. Data collection continued until the research team agreed that no new themes were generated (data saturation). Saturation was reached by the fourth interview, which supports that the participant sample, although small, was sufficiently robust to elucidate major themes. All interviews were recorded then transcribed verbatim and analysed (NVivo version 12; QSR International, Doncaster, Australia) using an inductive thematic approach. 6 Line-by-line coding identified themes and subthemes. The preliminary coding framework was refined through iterative discussion by the researchers (AS and JSK). A random sample of three transcripts was double coded (AS and JSK) and differences in coding were discussed until agreement was reached. Subsequently, all transcripts were systematically coded by one of us (AS). The study was reviewed and approved by the PaTH network and