Planners of interventional studies in psoriasis face the dilemma of selecting suitable quality-of-life (QoL) measures. Systematic reviews have the potential of identifying psychometrically sound measures in a given therapeutic area, while guiding the development of practice guidelines. The aim of this systematic review was to generate evidence of the use of QoL instruments in randomized controlled trials (RCTs) for interventions in psoriasis. The methodology followed the PRISMA guidelines. Six databases were searched with 388 search terms. Abstracts of articles were reviewed independently by two assessors, and a third adjudicator resolved any opinion differences. Risk of bias was assessed using the Jadad scale. Of 3646 screened publications, 99 articles (100 trials) met the eligibility criteria for inclusion, describing research on 33 215 patients. Thirty-three trials tested topical therapy, 18 systemic, 39 biologics, nine phototherapy and 10 other interventions. The Dermatology Life Quality Index (DLQI) was the most commonly used QoL instrument (83 studies, 83%), followed by the 36-Item Short Form Survey (SF-36) (31, 31%), EuroQoL-5D (EQ-5D) (15, 15%), Psoriasis Disability Index (14, 14%) and Skindex (five, 5%). There was widespread inconsistency in the way that QoL data were reported. Of the 100 trials identified, 37 reported minimal clinically important difference (MCID): 32 for DLQI, 10 for SF-36 and six for EQ-5D. QoL measurement is increasingly being reported in RCTs of psoriasis. Formal guidelines are needed for assessment and publishing of QoL data. Researchers should consider whether MCID information is available, and development of MCID data should be encouraged.

Interventions often result in statistically significant quality of life (QoL) improvement, but may not reach the threshold of clinical importance. The minimal clinically important difference (MCID) is the minimal score change of relevance clinically. We introduce the concept of 2MCID, a score change at least twice the usual threshold (i.e. 8 for DLQI), highlighting therapies changing by this higher threshold. A systematic review was conducted of the use of QoL instruments and of the impact of psoriasis treatments in randomized controlled trials (RCTs). 388 search terms were used to conduct searches in six databases adhering to PRISMA guidelines. Two assessors independently reviewed abstracts: a third resolved differences. Of 3646 screened publications, 99 articles (100 trials) involving 33,215 subjects met inclusion eligibility criteria. Of these 100 trials, 37 reported MCID; 32 DLQI, 10 SF-36 and 6 EQ-5D. 33 trials tested topical therapy, 18 systemic, 39 biologics, 9 phototherapy and 10 other interventions. For studies with treatment endpoint or assessment at 12 weeks, the interventions with the greatest average DLQI impact in each category were: Liquor Carbonis Distillate 15% (>1MCID, 5.8 pts), ciclosporin 3-5 mg/kg (>1MCID, 6.6 pts), secukinumab 300 mg (>2MCID, 11.4 pts), PUVAsol 0.6 mg/kg + isotretinoin 0.5 mg/kg (>2MCID, 11.2 pts) and educational programme (1MCID, 4 pts). Clolobetasol spray 0.05% (8 points, 4 weeks), ustekinumab 90 mg (8, 12), etanercept 50 mg (8.7, 24) and MTX 15 mg (8.7, 16) also reached 2MCID. The concept of '2MCID' adds meaning to score change when comparing therapies and results across different QoL instruments, though this requires further validation. However secukinumab and PUVAsol + isotretinoin both reached 2MCID at 12 weeks, according well with clinical experience.