Table 1. Types of candidate definitions for response criteria that were developed and tested.

Type of candidate definitions of response	Description	Example of the candidate definition for the response criteria
Previously published (categorical definition)	Previously published response criteria that were retested.	MINIMAL: 3 of any 6 improved by ≥ 20%; no more than 1 worse by > 30%; which cannot be CMAS (8) MODERATE: 3 of any 6 improved by ≥ 50%; no more than 1 worse by > 30%; which cannot be CMAS (9) MAJOR: 3 of any 6 improved by ≥ 70%; no more than 1 worse by > 30%; which cannot be CMAS (9)
Newly drafted (categorical definition)	Drafted relative or absolute percent change candidate definitions of response, based on recent CSM survey.	MINIMAL: MD Global, muscle strength (MMT or CMAS), and one other CSM improved by ≥20% MODERATE: MD Global, muscle strength (MMT or CMAS), and one other CSM improved by ≥30% MAJOR: MD Global, muscle strength (MMT or CMAS), and one other CSM improved by ≥50%
Weighted (categorical definition)	Applied conjoint-analysis relative weights to CSM in newly drafted definitions. Each CSM receives Improvement Points (corresponding relative weights), when it reaches the threshold for minimal, moderate, or major improvement. Worsening Points are applied similarly. Improvement is calculated based on a total score of improvement versus worsening.	Improvement = at least 3.5 Improvement Points out of 10 Total Improvement Points, and no more than 1.5 Worsening Points, where MD Global =2 points; Parent Global = 1 point; MMT/CMAS = 3 points; CHAQ = 1.5 points, ExtraMusc/DAS = 1.5 points, Enzyme/CHQ-PhS = 1 point MINIMAL: Improvement Points given when CSM ≥20%; Worsening Points given when CSM worse by >30% MODERATE: Improvement Points given when CSM ≥50%; Worsening Points given when CSM worse by >30% MAJOR: Improvement Points given when CSM ≥75%; Worsening Points given when CSM worse by >30%
Logistic regression (continuous definition)	Model of improvement using a combination of CSM with different weights, as developed in the logistic regression model. Total scores derived, with different cutoffs for minimal, moderate, and major improvement. Relative percent change.	Improvement Score = (MD Global % change) + 0.5 × (Parent Global Activity % change) + 0.5 × (ExtraMusc Activity or DAS % change) MINIMAL: Improvement Score ≥ 15 MODERATE: Improvement Score ≥ 30 MAJOR: Improvement Score ≥ 60
Core set measure-weighted* (continuous definition)	Multiply the percent change in each CSM by the weights derived from conjoint analysis. Then sum (% change in each CSM × conjoint analysis weights) to get final Total Improvement Score. Different thresholds for minimal, moderate, and major improvement established based on consensus profile ratings as gold standard.	Improvement Score = 2× (MD Global % change) + (Parent Global % change) + 3× (MMT or CMAS % change) + 1.5× (CHAQ % change) + 1.5× (ExtraMusc or DAS % change) + (Enzyme or CHQ-PhS % change) MINIMAL: Improvement Score ≥100 MODERATE: Improvement Score ≥250 MAJOR: Improvement Score ≥400
Conjoint analysis (continuous definition)	For a given range in the level of improvement in each CSM, a score is assigned, as developed by the survey results and modeling. Greater degrees of improvement receive higher scores. A patient is minimally improved if their Improvement Score is above the cutoff for minimal improvement; similarly for moderate and major improvement.	The full absolute percent change model is shown in Table 3 and in Supplementary Table 2, but the cut points for the model for JDM are: MINIMAL: Improvement Score ≥ 30 MODERATE: Improvement Score ≥45 MAJOR: Improvement Score ≥70

Abbreviations: CMAS, Childhood Myositis Assessment Scale; CSM, core set measure; MD Global, Physician Global Activity; MMT, manual muscle testing; Parent Global, Parent's Global Activity Score; CHAQ, Childhood Health Assessment Questionnaire; ExtraMusc, Extramuscular Global Activity; DAS, Disease Activity Score; Enzyme, most abnormal serum muscle enzyme value among aldolase, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and creatine kinase; CHQ-PhS, Physical Summary Score of the Child Health Questionnaire-Parent Form 50.

^*This type of definition was not brought to the final consensus conference.