John R Ingram, Pick‐Ngor Woo, Ser Ling Chua, Anthony D Ormerod, Nemesha Desai, Anneke C Kai, Kerry Hood, Tara Burton, Francisco Kerdel, Sarah E Garner, Vincent Piguet

Hidradenitis suppurativa (HS) is a chronic inflammatory skin condition characterised by recurrent painful boils in flexural sites, such as the axillae and groin, that affects about 1% of the population, with onset in early adulthood. To assess the effects of interventions for HS in people of all ages. We searched the following databases up to 13 August 2015: the Cochrane Skin Group Specialised Register, CENTRAL in the Cochrane Library (Issue 7, 2015), MEDLINE (from 1946), EMBASE (from 1974), and LILACS (from 1982). We also searched five trials registers and handsearched the conference proceedings of eight dermatology meetings. We checked the reference lists of included and excluded studies for further references to relevant trials. Randomised controlled trials (RCTs) of all interventions for hidradenitis suppurativa. Two review authors independently assessed study eligibility and methodological quality and performed data extraction. Our primary outcomes were quality of life, measured by a validated dermatology-specific scale, and adverse effects of the interventions. Twelve trials, with 615 participants, met our inclusion criteria. The median number of participants in each trial was 27, and median trial duration was 16 weeks. The included studies were conducted over a 32-year time period, from 1983 to 2015. A single RCT that was underpowered to detect clinically meaningful differences investigated most interventions.There were four trials of anti-TNF-α (tumour necrosis factor-alpha) therapies, which included etanercept, infliximab, and adalimumab. Adalimumab 40 mg weekly improved the Dermatology Life Quality Index (DLQI) score in participants with moderate to severe HS by 4.0 points relative to placebo (95% confidence interval (CI) -6.5 to -1.5 points), an effect size approximately equal to the DLQI minimal clinically important difference. We reduced the evidence quality to 'moderate' because the effect size was based on the results of only one study. In a meta-analysis of two studies with 124 participants, standard dose adalimumab 40 mg every other week was ineffective compared with placebo (moderate quality evidence). In a smaller study of 38 participants, of whom only 33 provided efficacy data, infliximab 5 mg/kg treatment improved DLQI by 8.4 DLQI points after eight weeks. Etanercept 50 mg twice weekly was well tolerated but ineffective.In a RCT of 200 participants, no difference was found in surgical complications (week one: risk ratio (RR) 0.78, 95% CI 0.58 to 1.05, moderate quality evidence) or risk of recurrence (after three months: RR 0.96, 95% CI 0.68 to 1.34, moderate quality evidence) in those randomised to receive a gentamicin-collagen sponge prior to primary closure compared with primary closure alone.RCTs of other interventions, including topical clindamycin 1% solution; oral tetracycline; oral ethinylestradiol 50 mcg with either cyproterone acetate 50 mg or norgestrel 500 mcg; intense pulsed light; neodymium-doped yttrium aluminium garnet (Nd:YAG) laser; methylene blue gel photodynamic therapy; and staphage lysate, were relatively small studies, preventing firm conclusions due to imprecision. Many knowledge gaps exist in RCT evidence for HS. Moderate quality evidence exists for adalimumab, which improves DLQI score when 40 mg is given weekly, twice the standard psoriasis dose. However, the 95% confidence interval includes an effect size of only 1.5 DLQI points, which may not be clinically relevant, and the safety profile of weekly dosing has not been fully established. Infliximab also improves quality of life, based on moderate quality evidence.More RCTs are needed in most areas of HS care, particularly oral treatments and the type and timing of surgical procedures. Outcomes should be validated, ideally, including a minimal clinically important difference for HS.