Validation of manual muscle testing and a subset of eight muscles for adult and juvenile idiopathic inflammatory myopathies.
OBJECTIVE
To validate manual muscle testing (MMT) for strength assessment in juvenile and adult dermatomyositis (DM) and polymyositis (PM).


METHODS
Patients with PM/DM (73 children and 45 adults) were assessed at baseline and reevaluated 6-9 months later. We compared Total MMT (a group of 24 proximal, distal, and axial muscles) and Proximal MMT (7 proximal muscle groups) tested bilaterally on a 0-10 scale with 144 subsets of 6 and 96 subsets of 8 muscle groups tested unilaterally. Expert consensus was used to rank the best abbreviated MMT subsets for face validity and ease of assessment.


RESULTS
The Total, Proximal, and best MMT subsets had excellent internal reliability (Total MMT r(s) = 0.91-0.98), and consistency (Cronbach's alpha = 0.78-0.97). Inter- and intrarater reliability were acceptable (Kendall's W 0.68-0.76, r(s) = 0.84-0.95). MMT subset scores correlated highly with Total and Proximal MMT scores and with the Childhood Myositis Assessment Scale, and correlated moderately with physician global activity, functional disability, magnetic resonance imaging, and axial and distal MMT scores, and, in adults, with creatine kinase level. The standardized response mean for Total MMT was 0.56 in juveniles and 0.75 in adults. Consensus was reached to use a subset of 8 muscles (neck flexors, deltoids, biceps, wrist extensors, gluteus maximus and medius, quadriceps, and ankle dorsiflexors) that performed as well as the Total and Proximal MMT, and had good face validity and ease of assessment.


CONCLUSIONS
These findings aid in standardizing the use of MMT for assessing strength as an outcome measure for myositis.
Rider
Lisa G
LG
Environmental Autoimmunity Group, Office of Clinical Research, National Institute of Environmental Health Sciences/NIH, 10 Center Drive, Bethesda, MD 20892-1301, USA. riderl@mail.nih.gov
Koziol
Deloris
D
Giannini
Edward H
EH
Jain
Minal S
MS
Smith
Michaele R
MR
Whitney-Mahoney
Kristi
K
Feldman
Brian M
BM
Wright
Susan J
SJ
Lindsley
Carol B
CB
Pachman
Lauren M
LM
Villalba
Maria L
ML
Lovell
Daniel J
DJ
Bowyer
Suzanne L
SL
Plotz
Paul H
PH
Miller
Frederick W
FW
Hicks
Jeanne E
JE
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003882:Dermatomyositis / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000175:diagnosis*; D009220:Myositis / Q000175:diagnosis; D015588:Observer Variation; D010808:Physical Examination; D017285:Polymyositis / Q000175:diagnosis*; D015203:Reproducibility of Results; D012720:Severity of Illness Index
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