Pediatric Rheumatology Online Journal → July 2003 → Dermatomyositis → Clinical Evaluation → Abstract #119

EVALUATION OF MUSCLE ASSESSMENT TOOLS IN JUVENILE DERMATOMYOSITIS

C. Pilkington,1 V. Farewell, J. Davidson, B. Feldman, A. Ravelli, R. Rennebohm, C. Ryder, S. Maillard, L. Rider

1Juvenile Dermatomyositis Research Centre, Institute of Child Health, London, United Kingdom; 2International Myositis Assessment & Clinical Studies Group

Six paediatric rheumatologists experienced in myositis evaluated 6 JDM patients in a workshop (2001) that was repeated one year later. On both occasions, the physicians received training in performance of two muscle strength and/or functional tools, the Childhood Myositis Assessment Scale (CMAS: max score 52) and an 8-muscle manual muscle test performed on the 0 10 point scale (MMT8: max score 80). The JDM patients ranged in age (3 12 years), disease duration (6 months 5 years), and MD global activity and damage scores (0.5 7.6 and 0 9.6 each).
2001 CMAS MMT 2002 CMAS MMT
patient mean(range) mean(range) patient mean(range) mean(range)
1 49 (48-50) 74 (68-76) 1 10 (none) 48 (43-54)
2 46 (none) 70 (60-75) 2 51 (50-52) 73 (70-74)
3 52 (51-52) 75 (72-79) 3 52 (none) 71 (68-76)
4 38 (37-40) 65 (58-71) 4 48 (47-49) 65 (63-67)
5 22 (21-23) 56 (53-58) 5 40 (38-41) 59 (56-64)
6 52 (none) 69 (63-74) 6 41 (40-42) 67 (59-68)
Using analysis of variance to examine rater agreement, there was little variation due to physicians (CMAS-0.06, MMT-0.7%) and most of the variation was due to the variation in patients (CMAS-99.8, MMT- 88%).
The scores for individual patients highlight that these 2 tools measure different parameters: patient 1 in 2002, a patient with multiple joint contractures, had a low CMAS score (10/52) and a moderate MMT (48/80). Other patients (3,6; 2, 3) had normal CMAS scores, but were mildly impaired in MMT.
The results demonstrate the high inter-physician agreement for muscle assessments using the CMAS and the MMT8. Differences in the degree of disability in these two measures highlight their complementary functions, with the CMAS capturing both muscle strength and stamina, whereas the MMT measures purely muscle strength. CMAS and MMT8 can be used in studies to help standardise JDM muscle assessments for both clinical trials and outcome studies.