<scp>EASI</scp> does it: a comparison of four eczema severity scales
Authors: K.S. Thomas
Journal: British Journal of Dermatology (2015)

Over the last 5 years, considerable efforts have been made to highlight the importance of core outcome sets within the field of medicine.1 It is possibly surprising that it took the research community quite so long to realize that there was a problem, and, more importantly, that a solution was within our grasp. How many times did we need to read systematic reviews stating that ‘it is not possible to combine the results of the included studies due to heterogeneity of trial design’, before someone took up the baton and pledged to do something about it? Thankfully, we now have some of the best methodological experts in the world working hard to develop guidance and support for groups working together to achieve consensus over core outcome sets for different medical conditions. The Core Outcome Measures in Effectiveness Trials (COMET) initiative (www.comet-initiative.org), established in 2010, maintains a database of resources and projects relevant to core outcome set development, and provides support for anyone wishing to get involved. Similarly, the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) initiative (www.cosmin.nl) provides guidance on how to select and evaluate clinical outcome measure instruments (or scales) for use in clinical trials. Within the field of dermatology, researchers have been proactive in this regard, and the COMET database now lists projects on core outcome sets for a range of conditions including eczema, acne, psoriasis, vitiligo, vulval skin disorders, cutaneous leishmaniasis and incontinence-associated dermatitis. Perhaps the most well-developed core outcomes initiative to date is that led by the Harmonising Outcome Measures for Eczema (HOME) initiative (www.homeforeczema.org), and the BJD has been following their progress with interest over the last 5 years.2-4 A core outcome set is simply a defined set of outcomes that have been agreed, by a broad range of stakeholders, to be the most important aspects of a disease to be measured in future clinical trials. These core aspects of the disease (known as domains) are the essential items that should be measured in all future trials, which, if measured consistently, will allow comparison of trial results and facilitate improved trial design. In the case of eczema, these domains have been defined as clinician-reported signs, patient-reported symptoms, quality of life and long-term control.3 Deciding which domains to measure is just the first step in defining a core outcome set. The next stages get much trickier. International consensus needs to be reached not only on ‘what should be measured’, but also on ‘how it should be measured’, ‘when it should be measured’ and ‘how the data should be presented and analysed’. In tackling decisions such as these, a systematic and evidence-based approach is needed. Only by understanding the specific measurement properties of the different scales will it be possible to agree upon a single preferred instrument for the future. However, choosing between different outcome measurement instruments can be very challenging with many potential options of scales, all of which contain similar but subtly different items. That is why studies such as the one reported in this month's BJD are so important.5 In this study by Zhao et al.,5 the four most commonly used clinician-rated eczema severity scales were tested head to head for the first time. These are objective Scoring Atopic Dermatitis (oSCORAD), Eczema Area and Severity Index (EASI), Six Area, Six Sign Atopic Dermatitis (SASSAD) and the Three Item Severity index (TIS). This study has allowed a comparative assessment of the different scales in terms of inter-rater and intrarater reliability, as well as assessment of how well the different scales correlate with patient-reported eczema severity and quality of life. Now, you might be forgiven for thinking that ‘surely such a simple study has been done many times before?’. But no – the scales have never been compared head to head, and it is pleasing that the results support the decision by the HOME initiative to recommend EASI as the preferred instrument for capturing clinician-reported eczema severity in future eczema trials.6 Tools and training materials are now available on the HOME website to facilitate uptake of EASI as the chosen core outcome instrument for capturing clinician-rated eczema severity, and the results have recently been published on the clinical interpretation of EASI scores.7 So the future of EASI is looking bright, but it is important that everyone involved in the design and conduct of eczema trials plays a part in ensuring that EASI is included as one of the chosen outcome measures in all future trials. This is already starting to happen, and new trials registered on the World Health Organization's Trials Registry Platform (www.who.int/ictrp) are showing an increase in the number of trials including EASI in their listed outcomes. Further work is needed to clarify at what time points EASI should be captured, and how best to summarize the data to facilitate comparison between trials. Beyond the topic of eczema, there is still much to be done in relation to dermatology outcomes research, and with over 2000 skin conditions to consider, this work may be ongoing for some time. Nevertheless, it is heartening that so many groups are now emerging to lead in developing core outcomes in different skin conditions, and the establishment of the Cochrane Skin Group Outcomes Research Initiative means that advice and support are now on hand to facilitate and share best practice.8 I look forward to the day when I can pick up a Cochrane Skin Group review and read that ‘all included trials were combined in a meaningful meta-analysis and that a clear answer is now available to guide clinical practice’. None declared.