Abstract: 　Objective　To investigate clinical application values of different assessment tools in evaluating the activity and severity of juvenile dermatomyositis (JDM). Methods: Clinical data of children diagnosed with JDM in Ren Ji Hospital Affiliated to Shanghai Jiao Tong University School of Medicine between January 2008 and September 2018 were collected, MDAAT (myositis disease activity assessment tool)/DAS (disease activity score)/CMAS (childhood myositis assessment scale) were performed to assess disease activity of JDM patients on the first day and after 24 - 48 h when they were in hospital. Results　Of these 35 JDM children, 2 with JPM, 4 with CADM, 29 with JDM, 15 children were male, and 20 were female, the female to male ratio was 1.33:1, and the average age at disease onset was 3.16±1.45 years, the elevation of serum levels of muscle enzymes at the disease onset was 50%～95.5%, the proportion of first symptoms onset with rash, muscle weakness, and both were 60%, 37%, 3%, respectively. Cronbach α values were all ＞0.8 for MDAAT, DAS, and CMAS, internal correlation coefficient for MDAAT, DAS, and CMAS was 0.940, 0.957, 0.942 (＞0.75), respectively；Construct validity was assessed by exploratory factor analysis according to the original questionnaires., which showed significant difference for scores between pre-therapy and post-therapy by MDAAT, DAS, and CMAS assessment (P<0.05). Conclusions　The assessment tools, including MDAAT, DAS, CMAS, have a good reliability, validity and responsiveness. The DAS is the shortest to get answers, which has great value in clinical practice.

Key words: 　juvenile;　dermatomyositis;　assessment tools;　reliability;　validity