title: Cross-sectional evaluation of electrical impedance myography and quantitative ultrasound for the assessment of Duchenne muscular dystrophy in a clinical trial setting.
abstract: BACKGROUND
  Electrical impedance myography and quantitative ultrasound are two noninvasive, painless, and effort-independent approaches for assessing neuromuscular disease. Both techniques have potential to serve as useful biomarkers in clinical trials in Duchenne muscular dystrophy. However, their comparative sensitivity to disease status and how they relate to one another are unknown.
  
  
  METHODS
  We performed a cross-sectional analysis of electrical impedance myography and quantitative ultrasound in 24 healthy boys and 24 with Duchenne muscular dystrophy, aged 2 to 14 years with trained research assistants performing all measurements. Three upper and three lower extremity muscles were studied unilaterally in each child, and the data averaged for each individual.
  
  
  RESULTS
  Both electrical impedance myography and quantitative ultrasound differentiated healthy boys from those with Duchenne muscular dystrophy (P < 0.001 for both). Quantitative ultrasound values correlated with age in Duchenne muscular dystrophy boys (rho = 0.45; P = 0.029), whereas electrical impedance myography did not (rho = -0.31; P = 0.14). However, electrical impedance myography phase correlated with age in healthy boys (rho = 0.51; P = 0.012), whereas quantitative ultrasound did not (rho = -0.021; P = 0.92). In Duchenne muscular dystrophy boys, electrical impedance myography phase correlated with the North Star Ambulatory Assessment (rho = 0.65; P = 0.022); quantitative ultrasound revealed a near-significant association (rho = -0.56; P = 0.060). The two technologies trended toward a moderate correlation with one another in the Duchenne muscular dystrophy cohort but not in the healthy group (rho = -0.40; P = 0.054 and rho = -0.32; P = 0.13, respectively).
  
  
  CONCLUSIONS
  Electrical impedance myography and quantitative ultrasound are complementary modalities for the assessment of boys with Duchenne muscular dystrophy; further study and application of these two modalities alone or in combination in a longitudinal fashion are warranted.
authors.affiliation: Division of Neuromuscular Diseases, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts. Electronic address: srutkove@bidmc.harvard.edu.
authors.forename: Seward B
authors.initials: SB
authors.lastname: Rutkove
authors.affiliation: Division of Neuromuscular Diseases, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
authors.forename: Tom R
authors.initials: TR
authors.lastname: Geisbush
authors.affiliation: Division of Neuromuscular Diseases, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Mijailovic
authors.affiliation: Division of Neuromuscular Diseases, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
authors.forename: Irina
authors.initials: I
authors.lastname: Shklyar
authors.affiliation: Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Amy
authors.initials: A
authors.lastname: Pasternak
authors.affiliation: Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Nicole
authors.initials: N
authors.lastname: Visyak
authors.affiliation: Division of Neuromuscular Diseases, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
authors.forename: Jim S
authors.initials: JS
authors.lastname: Wu
authors.affiliation: Department of Neurology, Washington University in St. Louis, St. Louis, Missouri.
authors.forename: Craig
authors.initials: C
authors.lastname: Zaidman
authors.affiliation: Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Basil T
authors.initials: BT
authors.lastname: Darras
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D020388:Muscular Dystrophy, Duchenne / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D009213:Myography; D013223:Statistics as Topic; D014463:Ultrasonography
keywords: Duchenne muscular dystrophy; biomarker; electrical impedance myography; outcome measure; quantitative ultrasound