2016 American College of Rheumatology / European League Against Rheumatism criteria for minimal, moderate and major clinical response for adult dermatomyositis and polymyositis: An International Myositis Assessment and Clinical Studies Group/Paediatric Rheumatology International Trials Organisation Collaborative Initiative

Objective. Develop response criteria for adult dermatomyositis (DM) and polymyositis (PM). Methods. Expert surveys, logistic regression, and conjoint analysis were used to develop 287 definitions using core set measures (CSM). Myositis experts rated greater improvement among multiple pair-wise scenarios in conjoint analysis surveys, where different levels of improvement in two CSM were presented. The PAPRIKA (Potentially All Pairwise Rankings of All Possible Alternatives) method determined relative weights of CSM and conjoint analysis definitions. Performance characteristics of definitions were evaluated on patient profiles using expert consensus (gold standard) and were validated using a clinical trial. Nominal group technique was used for consensus. Results. Consensus was reached for a conjoint analysis–based continuous model using absolute percentage change in CSMs (physician, patient, and extra-muscular global activity, muscle strength, health assessment questionnaire and muscle enzymes). A Total Improvement Score (0-100), determined by summing scores in each CSM, was based on the improvement and relative weight of each CSM. Thresholds for minimal, moderate, and major improvement were ≥20, ≥40, and ≥60 points in the Total Improvement Score. The same criteria were chosen for juvenile DM with different improvement thresholds. Sensitivity and specificity in DM/PM patient cohorts were 85% and 92%, 90% and 96%, and 90% and 96% for minimal, moderate, and major improvement, respectively. Definitions were validated in trial analysis for differentiating the physician rating of improvement (P<0.001). Conclusion. The response criteria for adult DM/PM was the conjoint analysis model based on absolute percentage change in six CSMs, with thresholds for minimal, moderate, and major improvement.