AB014. Developing classification criteria for skin-predominant dermatomyositis: assessing the methodology of the prospective validation study

The Dermatomyositis Delphi Criteria Project created 25 provisional clinical, laboratory and contextual classification criteria after an extensive literature search, three rounds of consensus exercises and nominal group discussions. These criteria will be subjected to a case-control validation study to create a combination of items that will define a more inclusive cohort of DM patients with skin-predominant disease for clinical research. Several measurement properties that need to be assessed prior to the conduct of a multicenter prospective validation study include the final purpose of the criteria set, population and disease characteristics of cases and controls for study entry, sources of samples, definition of criteria items, methods of item ranking and reduction, and consideration of criteria set validity against a comparator backdrop “gold standard” criteria. An expert committee Delphi and several online discussions among participants from the fields of dermatology, and adult and pediatric rheumatology have been conducted in order to address such issues. Constant evaluation of the methodologic process is vital to produce classification criteria which are valid and reliable to identify patients with DM and delineate these patients from those with mimicker diseases.