A narrative review of the definition of ‘flare’ in hidradenitis suppurativa

Background: Hidradenitis suppurativa (HS) is a chronic, inflammatory condition that can have periodic worsening or flares. Measurement of flare is important because it can inform treatment efficacy; however, it is unclear how HS flare should be defined. Objectives: This study reviewed the literature for definitions of HS flare. Methods: The PubMed MEDLINE online database was searched on 10 January 2018 and the search was repeated on 8 December 2018 for new publications. Titles and abstracts were screened for inclusion. Subsequently, full articles were screened for inclusion. Papers were included if the publication was a systematic review, clinical trial, cohort study, case report or series, or cross-sectional study. Studies were excluded if they were journalistic reviews, did not discuss clinical findings of HS or did not use the words ‘flare’, ‘exacerbation’, ‘relapse’ or ‘recurrence’. Results: Two hundred and seventy-four papers were identified and 154 fulfilled the study criteria. Of these, 27 (17.5%) included the term ‘flare’ and 16 (10.4%) included the term ‘exacerbation’. Two of the 27 papers (7%) defined the term flare and both included patient report of changes in symptoms or signs. One of 16 papers (6%) defined exacerbation, which was taken as one new HS lesion. The terms ‘recurrence’ and ‘relapse’ were more apt to be defined: 13% (13 of 100) and 14% (six of 44), respectively. Conclusions :The lack of a specific and measurable definition of HS flare is a barrier to assessment of this important outcome. Once a specific and measurable definition is established, validated and reliable measures of HS flare can be incorporated into future studies.SCOPUS: ar.j