A narrative review of the definition of 'flare' in hidradenitis suppurativa.

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. What's already known about this topic? Hidradenitis suppurativa (HS) is a chronic, relapsing inflammatory skin condition. The ability to assess flares is important to people who have HS; however, it is unclear how this is defined. HS flare is one of the core outcomes in the core outcome set for HS clinical trials; however, it is unclear how this should be assessed. What does this study add? This literature review reveals the paucity of measurable definitions associated with the use of the term 'flare' in the HS literature. It also highlights the variation and lack of a validated and reliable measure of HS flare.