Has the core outcome (domain) set for vitiligo been implemented? An updated systematic review on outcomes and outcome measures in vitiligo randomized clinical trials

In 2015, a major achievement in vitiligo research was the development of an internationally agreed upon core outcome domain set for randomized clinical trials (RCTs). Three outcomes were identified as being essential: repigmentation, side-effects/harms and maintenance of gained repigmentation. Four items were further recommended for inclusion. The following recommendations then followed: repigmentation should be assessed by measuring the percentage of repigmentation in quartiles (0-25%, 26-50%, 51-79%, 80-100%) and cosmetic acceptability of the results should be assessed using the Vitiligo Noticeability Scale. The primary objective of this study was to assess uptake of the core outcome domain set for RCTs in vitiligo. Secondary objectives were to update the systematic review on outcomes reported in vitiligo RCTs, and to assess whether repigmentation and cosmetic acceptability of the results were measured using the above-mentioned recommended scales. We searched PubMed, Cochrane Library (CENTRAL and Systematic Reviews) and ClinicalTrials.gov for vitiligo RCTs between November 2009 and March 2021. Screening and data extraction were independently performed on title and summary by two researchers. All outcomes and outcome measures reported in eligible RCTs were retrieved and collated. In total, 174 RCTs were identified: 62 were published between 2009 and 2015, and 112 were published between 2016 and 2021.Thirty-eight different outcomes were reported. Repigmentation was the primary outcome in 89% of trials (150 of 169). Forty-nine different tools were used to measure repigmentation. Side-effects and harms were reported in 78% of trials (136 of 174). Maintenance of gained repigmentation was reported in only 11% of trials (20 of 174) and duration of follow-up varied greatly from 1 to 14 months. Cosmetic acceptability of the results and cessation of disease activity were assessed in only 2% of trials (four of 174). Quality of life of patients with vitiligo was assessed in 13% of trials (22 of 174). Finally, only 11 of 112 RCTs (10%) published between 2016 and 2021 reported all three essential core outcome domains (repigmentation, side-effects and maintenance of gained repigmentation) and none of the trials reported both essential and recommended core outcome domains. Efforts are still needed to close the gap between set recommendations and RCT outcome reporting.