title: Comparison of 3 instruments to measure muscle strength in children: A prospective study.
abstract: OBJECTIVE
  To establish which instrument is the most valid and reliable measure of muscle strength in children aged 4-11 years and can improve the diagnostic procedure in children with suspected myopathy to spare more of them from muscle biopsy.
  
  
  METHODS
  In a prospective study over a 2 year period, 22 patients aged 4-11 years were recruited. They had all been referred to our specialist centre on the suspicion of myopathy. Hand-held dynamometry, the Jamar dynamometer and a new Motor Performance Test were administered before muscle biopsy. Validity was assessed by the power to discriminate between patients with and without myopathy using logistic regression analysis and receiver operating characteristic (ROC) analysis. The area under the ROC curve (AUC) was calculated as a measure of the diagnostic power.
  
  
  RESULTS
  Comparison of the three instruments showed that the Motor Performance Test had the highest validity. Hand-held dynamometry generally had lower validity and showed wide variation in the 11 muscle groups. The Jamar dynamometer had very low validity in early stage myopathy.
  
  
  CONCLUSIONS
  The Motor Performance Test was the most valid and reliable instrument to indicate the presence of myopathy in children. This objective, non-invasive and child-friendly instrument can improve the diagnostic procedure and exclude more children without myopathy from muscle biopsy.
authors: Department of Rehabilitation Medicine (HP 898), University Medical Centre Nijmegen St Radboud, PO Box 9101, 6500 HB Nijmegen, The Netherlands. w.vandenbeld@reval.umcn.nl
authors: Willeke A
authors: WA
authors: Van den Beld
authors: Gitty A C
authors: GA
authors: Van der Sanden
authors: Anjo J W M
authors: AJ
authors: Janssen
authors: Rob C A
authors: RC
authors: Sengers
authors: André L M
authors: AL
authors: Verbeek
authors: Fons J M
authors: FJ
authors: Gabreëls
mesh_terms: D002648:Child; D002675:Child, Preschool; D004576:Electromyography; D005260:Female; D006225:Hand / Q000294:innervation; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D009135:Muscular Diseases / Q000175:diagnosis* / Q000503:physiopathology*; D010808:Physical Examination; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity