A systematic review of 454 randomized controlled trials using the Dermatology Life Quality Index: experience in 69 diseases and 43 countries.

Background: Over 29 years of clinical application, the Dermatology Life Quality Index (DLQI) has remained the most used patient-reported outcome (PRO) in dermatology due to its robustness, simplicity and ease of use.
Objectives: To generate further evidence of the DLQI's utility in randomized controlled trials (RCTs) and to cover all diseases and interventions.
Methods: The methodology followed PRISMA guidelines and included seven bibliographical databases, searching articles published from 1 January 1994 until 16 November 2021. Articles were reviewed independently by two assessors, and an adjudicator resolved any opinion differences.
Results: Of 3220 screened publications, 454 articles meeting the eligibility criteria for inclusion, describing research on 198 190 patients, were analysed. DLQI scores were primary endpoints in 24 (5.3%) of studies. Most studies were of psoriasis (54.1%), although 69 different diseases were studied. Most study drugs were systemic (85.1%), with biologics comprising 55.9% of all pharmacological interventions. Topical treatments comprised 17.0% of total pharmacological interventions. Nonpharmacological interventions, mainly laser therapy and ultraviolet radiation treatment, comprised 12.2% of the total number of interventions. The majority of studies (63.7%) were multicentric, with trials conducted in at least 42 different countries; 40.2% were conducted in multiple countries. The minimal clinically importance difference (MCID) was reported in the analysis of 15.0% of studies, but only 1.3% considered full score meaning banding of the DLQI. Forty-seven (10.4%) of the studies investigated statistical correlation of the DLQI with clinical severity assessment or other PRO/quality of life tools; and 61-86% of studies had within-group scores differences greater than the MCID in 'active treatment arms'. The Jadad risk-of-bias scale showed that bias was generally low, as 91.8% of the studies had Jadad scores of ≥ 3; only 0.4% of studies showed a high risk of bias from randomization. Thirteen per cent had a high risk of bias from blinding and 10.1% had a high risk of bias from unknown outcomes of all participants in the studies. In 18.5% of the studies the authors declared that they followed an intention-to-treat protocol; imputation for missing DLQI data was used in 34.4% of studies.
Conclusions: This systematic review provides a wealth of evidence of the use of the DLQI in clinical trials to inform researchers' and -clinicians' decisions for its further use. Recommendations are also made for improving the reporting of data from future RCTs using the DLQI.
Competing Interests: Conflicts of interest J.V. has participated in an Advisory Board for Amgen, has received payment or honoraria from L’Oréal and support from UCB Pharma for attending meetings. F.M.A. has received honoraria from AbbVie, Janssen, LEO Pharma, Lilly Pharmaceuticals, L’Oréal, Novartis and UCB. His department receives income from royalties from the Dermatology Life Quality Index (DLQI) and related instruments. J.R.I. receives a stipend as Editor-in-Chief of the British Journal of Dermatology and an authorship honorarium from UpToDate. He is a consultant for Boehringer Ingelheim, ChemoCentryx, Citryll, Novartis and UCB Pharma, and has served on advisory boards for Insmed, Kymera Therapeutics and Viela Bio. He is co-­copyright holder of HiSQOL, Investigator Global Assessment and Patient Global Assessment instruments for hidradenitis suppurativa. His department receives income from royalties from the DLQI and related instruments. S.S. has received an unrestricted educational grant from GSK, is a consultant for Novo Nordisk and produces educational materials for AbbVie. A.Y.F. is joint copyright owner of the DLQI. Cardiff University receives royalties from some use of the DLQI; A.Y.F. receives a proportion of these under standard university policy. J.R.J. and R.K.S. report no conflicts of interest.
(© The Author(s) 2023. Published by Oxford University Press on behalf of British Association of Dermatologists.)