VALIDATION DATA

Spearman’s correlation was excellent for proximal MMT and MMT8 scores compared with the total MMT score in patients with treatment-refractory adult PM/DM (Spearman’s r ⫽ 0.91– 0.96) and 73 juvenile idiopathic inflammatory myopathy patients from a natural history study (Spearman’s r ⫽ 0.96 – 0.98) (11). Internal consistency, measured by Cronbach’s a, was also very good to excellent for total, proximal, and MMT8 scores, ranging from 0.79 – 0.93 in adult PM/DM and from 0.90–0.93 in juvenile idiopathic inflammatory myopathy.

In a study of juvenile IIM patients who were evaluated by 1 pediatric physical therapist in the morning and again in the afternoon, the Spearman’s rank correlation coefficient for the total, proximal, distal, and MMT8 scores for each pair ranged from 0.8 –0.95 (all P < 0.001). 

Interrater reliability was very good, with Kendall’s W ranging from 0.71– 0.76 for total, proximal, and MMT8 scores

In developing the MMT8, a group of adult and pediatric rheumatologists and physical therapists agreed upon 3 possible combinations of 8 proximal, distal, and axial muscle groups that closely approximate a total MMT score and could be used in the clinic or in research settings for patients with juvenile and adult DM and PM.